diff --git a/.flake8 b/.flake8
new file mode 100644
index 0000000..e4e5eb3
--- /dev/null
+++ b/.flake8
@@ -0,0 +1,3 @@
+[flake8]
+max-line-length = 88
+extend-ignore = E203, W503
diff --git a/Makefile b/Makefile
index 9e46488..6b6ed3d 100644
--- a/Makefile
+++ b/Makefile
@@ -2,6 +2,13 @@
 help: ## List make targets
 	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-30s\033[0m %s\n", $$1, $$2}'
 
+lint: ## Lint source code
+	poetry run flake8
+
+format: ## Format source code
+	poetry run isort .
+	poetry run black .
+
 .PHONY: test
 test: ## Run tests
 	poetry run pytest
diff --git a/poetry.lock b/poetry.lock
index b0a2fd5..33e32d9 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -1,3 +1,11 @@
+[[package]]
+name = "appdirs"
+version = "1.4.4"
+description = "A small Python module for determining appropriate platform-specific dirs, e.g. a \"user data dir\"."
+category = "dev"
+optional = false
+python-versions = "*"
+
 [[package]]
 name = "atomicwrites"
 version = "1.4.0"
@@ -20,6 +28,28 @@ docs = ["furo", "sphinx", "zope.interface"]
 tests = ["coverage[toml] (>=5.0.2)", "hypothesis", "pympler", "pytest (>=4.3.0)", "six", "zope.interface"]
 tests_no_zope = ["coverage[toml] (>=5.0.2)", "hypothesis", "pympler", "pytest (>=4.3.0)", "six"]
 
+[[package]]
+name = "black"
+version = "20.8b1"
+description = "The uncompromising code formatter."
+category = "dev"
+optional = false
+python-versions = ">=3.6"
+
+[package.dependencies]
+appdirs = "*"
+click = ">=7.1.2"
+mypy-extensions = ">=0.4.3"
+pathspec = ">=0.6,<1"
+regex = ">=2020.1.8"
+toml = ">=0.10.1"
+typed-ast = ">=1.4.0"
+typing-extensions = ">=3.7.4"
+
+[package.extras]
+colorama = ["colorama (>=0.4.3)"]
+d = ["aiohttp (>=3.3.2)", "aiohttp-cors"]
+
 [[package]]
 name = "certifi"
 version = "2020.12.5"
@@ -36,6 +66,14 @@ category = "main"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"
 
+[[package]]
+name = "click"
+version = "7.1.2"
+description = "Composable command line interface toolkit"
+category = "dev"
+optional = false
+python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"
+
 [[package]]
 name = "colorama"
 version = "0.4.4"
@@ -44,6 +82,19 @@ category = "dev"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"
 
+[[package]]
+name = "flake8"
+version = "3.9.1"
+description = "the modular source code checker: pep8 pyflakes and co"
+category = "dev"
+optional = false
+python-versions = "!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,!=3.4.*,>=2.7"
+
+[package.dependencies]
+mccabe = ">=0.6.0,<0.7.0"
+pycodestyle = ">=2.7.0,<2.8.0"
+pyflakes = ">=2.3.0,<2.4.0"
+
 [[package]]
 name = "idna"
 version = "2.10"
@@ -60,6 +111,19 @@ category = "dev"
 optional = false
 python-versions = "*"
 
+[[package]]
+name = "isort"
+version = "5.8.0"
+description = "A Python utility / library to sort Python imports."
+category = "dev"
+optional = false
+python-versions = ">=3.6,<4.0"
+
+[package.extras]
+pipfile_deprecated_finder = ["pipreqs", "requirementslib"]
+requirements_deprecated_finder = ["pipreqs", "pip-api"]
+colors = ["colorama (>=0.4.3,<0.5.0)"]
+
 [[package]]
 name = "lxml"
 version = "4.6.2"
@@ -74,6 +138,22 @@ html5 = ["html5lib"]
 htmlsoup = ["beautifulsoup4"]
 source = ["Cython (>=0.29.7)"]
 
+[[package]]
+name = "mccabe"
+version = "0.6.1"
+description = "McCabe checker, plugin for flake8"
+category = "dev"
+optional = false
+python-versions = "*"
+
+[[package]]
+name = "mypy-extensions"
+version = "0.4.3"
+description = "Experimental type system extensions for programs checked with the mypy typechecker."
+category = "dev"
+optional = false
+python-versions = "*"
+
 [[package]]
 name = "packaging"
 version = "20.9"
@@ -85,6 +165,14 @@ python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
 [package.dependencies]
 pyparsing = ">=2.0.2"
 
+[[package]]
+name = "pathspec"
+version = "0.8.1"
+description = "Utility library for gitignore style pattern matching of file paths."
+category = "dev"
+optional = false
+python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"
+
 [[package]]
 name = "pluggy"
 version = "0.13.1"
@@ -104,6 +192,22 @@ category = "dev"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
 
+[[package]]
+name = "pycodestyle"
+version = "2.7.0"
+description = "Python style guide checker"
+category = "dev"
+optional = false
+python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
+
+[[package]]
+name = "pyflakes"
+version = "2.3.1"
+description = "passive checker of Python programs"
+category = "dev"
+optional = false
+python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
+
 [[package]]
 name = "pyparsing"
 version = "2.4.7"
@@ -133,6 +237,14 @@ toml = "*"
 [package.extras]
 testing = ["argcomplete", "hypothesis (>=3.56)", "mock", "nose", "requests", "xmlschema"]
 
+[[package]]
+name = "regex"
+version = "2021.4.4"
+description = "Alternative regular expression module, to replace re."
+category = "dev"
+optional = false
+python-versions = "*"
+
 [[package]]
 name = "requests"
 version = "2.25.1"
@@ -159,6 +271,22 @@ category = "dev"
 optional = false
 python-versions = ">=2.6, !=3.0.*, !=3.1.*, !=3.2.*"
 
+[[package]]
+name = "typed-ast"
+version = "1.4.3"
+description = "a fork of Python 2 and 3 ast modules with type comment support"
+category = "dev"
+optional = false
+python-versions = "*"
+
+[[package]]
+name = "typing-extensions"
+version = "3.7.4.3"
+description = "Backported and Experimental Type Hints for Python 3.5+"
+category = "dev"
+optional = false
+python-versions = "*"
+
 [[package]]
 name = "urllib3"
 version = "1.26.3"
@@ -175,9 +303,13 @@ socks = ["PySocks (>=1.5.6,!=1.5.7,<2.0)"]
 [metadata]
 lock-version = "1.1"
 python-versions = "^3.9"
-content-hash = "762cefef0b6dae37983d4a0fbc483fec0da8ba9424e625c5ca49d85f6ec8d9a1"
+content-hash = "d43dc5e9f04655ee9faaa2e1fc46c006de7509945c4a0e6c4ea3990081f17d4e"
 
 [metadata.files]
+appdirs = [
+    {file = "appdirs-1.4.4-py2.py3-none-any.whl", hash = "sha256:a841dacd6b99318a741b166adb07e19ee71a274450e68237b4650ca1055ab128"},
+    {file = "appdirs-1.4.4.tar.gz", hash = "sha256:7d5d0167b2b1ba821647616af46a749d1c653740dd0d2415100fe26e27afdf41"},
+]
 atomicwrites = [
     {file = "atomicwrites-1.4.0-py2.py3-none-any.whl", hash = "sha256:6d1784dea7c0c8d4a5172b6c620f40b6e4cbfdf96d783691f2e1302a7b88e197"},
     {file = "atomicwrites-1.4.0.tar.gz", hash = "sha256:ae70396ad1a434f9c7046fd2dd196fc04b12f9e91ffb859164193be8b6168a7a"},
@@ -186,6 +318,9 @@ attrs = [
     {file = "attrs-20.3.0-py2.py3-none-any.whl", hash = "sha256:31b2eced602aa8423c2aea9c76a724617ed67cf9513173fd3a4f03e3a929c7e6"},
     {file = "attrs-20.3.0.tar.gz", hash = "sha256:832aa3cde19744e49938b91fea06d69ecb9e649c93ba974535d08ad92164f700"},
 ]
+black = [
+    {file = "black-20.8b1.tar.gz", hash = "sha256:1c02557aa099101b9d21496f8a914e9ed2222ef70336404eeeac8edba836fbea"},
+]
 certifi = [
     {file = "certifi-2020.12.5-py2.py3-none-any.whl", hash = "sha256:719a74fb9e33b9bd44cc7f3a8d94bc35e4049deebe19ba7d8e108280cfd59830"},
     {file = "certifi-2020.12.5.tar.gz", hash = "sha256:1a4995114262bffbc2413b159f2a1a480c969de6e6eb13ee966d470af86af59c"},
@@ -194,10 +329,18 @@ chardet = [
     {file = "chardet-4.0.0-py2.py3-none-any.whl", hash = "sha256:f864054d66fd9118f2e67044ac8981a54775ec5b67aed0441892edb553d21da5"},
     {file = "chardet-4.0.0.tar.gz", hash = "sha256:0d6f53a15db4120f2b08c94f11e7d93d2c911ee118b6b30a04ec3ee8310179fa"},
 ]
+click = [
+    {file = "click-7.1.2-py2.py3-none-any.whl", hash = "sha256:dacca89f4bfadd5de3d7489b7c8a566eee0d3676333fbb50030263894c38c0dc"},
+    {file = "click-7.1.2.tar.gz", hash = "sha256:d2b5255c7c6349bc1bd1e59e08cd12acbbd63ce649f2588755783aa94dfb6b1a"},
+]
 colorama = [
     {file = "colorama-0.4.4-py2.py3-none-any.whl", hash = "sha256:9f47eda37229f68eee03b24b9748937c7dc3868f906e8ba69fbcbdd3bc5dc3e2"},
     {file = "colorama-0.4.4.tar.gz", hash = "sha256:5941b2b48a20143d2267e95b1c2a7603ce057ee39fd88e7329b0c292aa16869b"},
 ]
+flake8 = [
+    {file = "flake8-3.9.1-py2.py3-none-any.whl", hash = "sha256:3b9f848952dddccf635be78098ca75010f073bfe14d2c6bda867154bea728d2a"},
+    {file = "flake8-3.9.1.tar.gz", hash = "sha256:1aa8990be1e689d96c745c5682b687ea49f2e05a443aff1f8251092b0014e378"},
+]
 idna = [
     {file = "idna-2.10-py2.py3-none-any.whl", hash = "sha256:b97d804b1e9b523befed77c48dacec60e6dcb0b5391d57af6a65a312a90648c0"},
     {file = "idna-2.10.tar.gz", hash = "sha256:b307872f855b18632ce0c21c5e45be78c0ea7ae4c15c828c20788b26921eb3f6"},
@@ -206,6 +349,10 @@ iniconfig = [
     {file = "iniconfig-1.1.1-py2.py3-none-any.whl", hash = "sha256:011e24c64b7f47f6ebd835bb12a743f2fbe9a26d4cecaa7f53bc4f35ee9da8b3"},
     {file = "iniconfig-1.1.1.tar.gz", hash = "sha256:bc3af051d7d14b2ee5ef9969666def0cd1a000e121eaea580d4a313df4b37f32"},
 ]
+isort = [
+    {file = "isort-5.8.0-py3-none-any.whl", hash = "sha256:2bb1680aad211e3c9944dbce1d4ba09a989f04e238296c87fe2139faa26d655d"},
+    {file = "isort-5.8.0.tar.gz", hash = "sha256:0a943902919f65c5684ac4e0154b1ad4fac6dcaa5d9f3426b732f1c8b5419be6"},
+]
 lxml = [
     {file = "lxml-4.6.2-cp27-cp27m-macosx_10_9_x86_64.whl", hash = "sha256:a9d6bc8642e2c67db33f1247a77c53476f3a166e09067c0474facb045756087f"},
     {file = "lxml-4.6.2-cp27-cp27m-manylinux1_i686.whl", hash = "sha256:791394449e98243839fa822a637177dd42a95f4883ad3dec2a0ce6ac99fb0a9d"},
@@ -245,10 +392,22 @@ lxml = [
     {file = "lxml-4.6.2-cp39-cp39-win_amd64.whl", hash = "sha256:535332fe9d00c3cd455bd3dd7d4bacab86e2d564bdf7606079160fa6251caacf"},
     {file = "lxml-4.6.2.tar.gz", hash = "sha256:cd11c7e8d21af997ee8079037fff88f16fda188a9776eb4b81c7e4c9c0a7d7fc"},
 ]
+mccabe = [
+    {file = "mccabe-0.6.1-py2.py3-none-any.whl", hash = "sha256:ab8a6258860da4b6677da4bd2fe5dc2c659cff31b3ee4f7f5d64e79735b80d42"},
+    {file = "mccabe-0.6.1.tar.gz", hash = "sha256:dd8d182285a0fe56bace7f45b5e7d1a6ebcbf524e8f3bd87eb0f125271b8831f"},
+]
+mypy-extensions = [
+    {file = "mypy_extensions-0.4.3-py2.py3-none-any.whl", hash = "sha256:090fedd75945a69ae91ce1303b5824f428daf5a028d2f6ab8a299250a846f15d"},
+    {file = "mypy_extensions-0.4.3.tar.gz", hash = "sha256:2d82818f5bb3e369420cb3c4060a7970edba416647068eb4c5343488a6c604a8"},
+]
 packaging = [
     {file = "packaging-20.9-py2.py3-none-any.whl", hash = "sha256:67714da7f7bc052e064859c05c595155bd1ee9f69f76557e21f051443c20947a"},
     {file = "packaging-20.9.tar.gz", hash = "sha256:5b327ac1320dc863dca72f4514ecc086f31186744b84a230374cc1fd776feae5"},
 ]
+pathspec = [
+    {file = "pathspec-0.8.1-py2.py3-none-any.whl", hash = "sha256:aa0cb481c4041bf52ffa7b0d8fa6cd3e88a2ca4879c533c9153882ee2556790d"},
+    {file = "pathspec-0.8.1.tar.gz", hash = "sha256:86379d6b86d75816baba717e64b1a3a3469deb93bb76d613c9ce79edc5cb68fd"},
+]
 pluggy = [
     {file = "pluggy-0.13.1-py2.py3-none-any.whl", hash = "sha256:966c145cd83c96502c3c3868f50408687b38434af77734af1e9ca461a4081d2d"},
     {file = "pluggy-0.13.1.tar.gz", hash = "sha256:15b2acde666561e1298d71b523007ed7364de07029219b604cf808bfa1c765b0"},
@@ -257,6 +416,14 @@ py = [
     {file = "py-1.10.0-py2.py3-none-any.whl", hash = "sha256:3b80836aa6d1feeaa108e046da6423ab8f6ceda6468545ae8d02d9d58d18818a"},
     {file = "py-1.10.0.tar.gz", hash = "sha256:21b81bda15b66ef5e1a777a21c4dcd9c20ad3efd0b3f817e7a809035269e1bd3"},
 ]
+pycodestyle = [
+    {file = "pycodestyle-2.7.0-py2.py3-none-any.whl", hash = "sha256:514f76d918fcc0b55c6680472f0a37970994e07bbb80725808c17089be302068"},
+    {file = "pycodestyle-2.7.0.tar.gz", hash = "sha256:c389c1d06bf7904078ca03399a4816f974a1d590090fecea0c63ec26ebaf1cef"},
+]
+pyflakes = [
+    {file = "pyflakes-2.3.1-py2.py3-none-any.whl", hash = "sha256:7893783d01b8a89811dd72d7dfd4d84ff098e5eed95cfa8905b22bbffe52efc3"},
+    {file = "pyflakes-2.3.1.tar.gz", hash = "sha256:f5bc8ecabc05bb9d291eb5203d6810b49040f6ff446a756326104746cc00c1db"},
+]
 pyparsing = [
     {file = "pyparsing-2.4.7-py2.py3-none-any.whl", hash = "sha256:ef9d7589ef3c200abe66653d3f1ab1033c3c419ae9b9bdb1240a85b024efc88b"},
     {file = "pyparsing-2.4.7.tar.gz", hash = "sha256:c203ec8783bf771a155b207279b9bccb8dea02d8f0c9e5f8ead507bc3246ecc1"},
@@ -265,6 +432,49 @@ pytest = [
     {file = "pytest-6.2.2-py3-none-any.whl", hash = "sha256:b574b57423e818210672e07ca1fa90aaf194a4f63f3ab909a2c67ebb22913839"},
     {file = "pytest-6.2.2.tar.gz", hash = "sha256:9d1edf9e7d0b84d72ea3dbcdfd22b35fb543a5e8f2a60092dd578936bf63d7f9"},
 ]
+regex = [
+    {file = "regex-2021.4.4-cp36-cp36m-macosx_10_9_x86_64.whl", hash = "sha256:619d71c59a78b84d7f18891fe914446d07edd48dc8328c8e149cbe0929b4e000"},
+    {file = "regex-2021.4.4-cp36-cp36m-manylinux1_i686.whl", hash = "sha256:47bf5bf60cf04d72bf6055ae5927a0bd9016096bf3d742fa50d9bf9f45aa0711"},
+    {file = "regex-2021.4.4-cp36-cp36m-manylinux1_x86_64.whl", hash = "sha256:281d2fd05555079448537fe108d79eb031b403dac622621c78944c235f3fcf11"},
+    {file = "regex-2021.4.4-cp36-cp36m-manylinux2010_i686.whl", hash = "sha256:bd28bc2e3a772acbb07787c6308e00d9626ff89e3bfcdebe87fa5afbfdedf968"},
+    {file = "regex-2021.4.4-cp36-cp36m-manylinux2010_x86_64.whl", hash = "sha256:7c2a1af393fcc09e898beba5dd59196edaa3116191cc7257f9224beaed3e1aa0"},
+    {file = "regex-2021.4.4-cp36-cp36m-manylinux2014_aarch64.whl", hash = "sha256:c38c71df845e2aabb7fb0b920d11a1b5ac8526005e533a8920aea97efb8ec6a4"},
+    {file = "regex-2021.4.4-cp36-cp36m-manylinux2014_i686.whl", hash = "sha256:96fcd1888ab4d03adfc9303a7b3c0bd78c5412b2bfbe76db5b56d9eae004907a"},
+    {file = "regex-2021.4.4-cp36-cp36m-manylinux2014_x86_64.whl", hash = "sha256:ade17eb5d643b7fead300a1641e9f45401c98eee23763e9ed66a43f92f20b4a7"},
+    {file = "regex-2021.4.4-cp36-cp36m-win32.whl", hash = "sha256:e8e5b509d5c2ff12f8418006d5a90e9436766133b564db0abaec92fd27fcee29"},
+    {file = "regex-2021.4.4-cp36-cp36m-win_amd64.whl", hash = "sha256:11d773d75fa650cd36f68d7ca936e3c7afaae41b863b8c387a22aaa78d3c5c79"},
+    {file = "regex-2021.4.4-cp37-cp37m-macosx_10_9_x86_64.whl", hash = "sha256:d3029c340cfbb3ac0a71798100ccc13b97dddf373a4ae56b6a72cf70dfd53bc8"},
+    {file = "regex-2021.4.4-cp37-cp37m-manylinux1_i686.whl", hash = "sha256:18c071c3eb09c30a264879f0d310d37fe5d3a3111662438889ae2eb6fc570c31"},
+    {file = "regex-2021.4.4-cp37-cp37m-manylinux1_x86_64.whl", hash = "sha256:4c557a7b470908b1712fe27fb1ef20772b78079808c87d20a90d051660b1d69a"},
+    {file = "regex-2021.4.4-cp37-cp37m-manylinux2010_i686.whl", hash = "sha256:01afaf2ec48e196ba91b37451aa353cb7eda77efe518e481707e0515025f0cd5"},
+    {file = "regex-2021.4.4-cp37-cp37m-manylinux2010_x86_64.whl", hash = "sha256:3a9cd17e6e5c7eb328517969e0cb0c3d31fd329298dd0c04af99ebf42e904f82"},
+    {file = "regex-2021.4.4-cp37-cp37m-manylinux2014_aarch64.whl", hash = "sha256:90f11ff637fe8798933fb29f5ae1148c978cccb0452005bf4c69e13db951e765"},
+    {file = "regex-2021.4.4-cp37-cp37m-manylinux2014_i686.whl", hash = "sha256:919859aa909429fb5aa9cf8807f6045592c85ef56fdd30a9a3747e513db2536e"},
+    {file = "regex-2021.4.4-cp37-cp37m-manylinux2014_x86_64.whl", hash = "sha256:339456e7d8c06dd36a22e451d58ef72cef293112b559010db3d054d5560ef439"},
+    {file = "regex-2021.4.4-cp37-cp37m-win32.whl", hash = "sha256:67bdb9702427ceddc6ef3dc382455e90f785af4c13d495f9626861763ee13f9d"},
+    {file = "regex-2021.4.4-cp37-cp37m-win_amd64.whl", hash = "sha256:32e65442138b7b76dd8173ffa2cf67356b7bc1768851dded39a7a13bf9223da3"},
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+    {file = "regex-2021.4.4-cp39-cp39-manylinux2014_x86_64.whl", hash = "sha256:fd45ff9293d9274c5008a2054ecef86a9bfe819a67c7be1afb65e69b405b3042"},
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+    {file = "regex-2021.4.4-cp39-cp39-win_amd64.whl", hash = "sha256:97f29f57d5b84e73fbaf99ab3e26134e6687348e95ef6b48cfd2c06807005a07"},
+    {file = "regex-2021.4.4.tar.gz", hash = "sha256:52ba3d3f9b942c49d7e4bc105bb28551c44065f139a65062ab7912bef10c9afb"},
+]
 requests = [
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@@ -273,6 +483,43 @@ toml = [
     {file = "toml-0.10.2-py2.py3-none-any.whl", hash = "sha256:806143ae5bfb6a3c6e736a764057db0e6a0e05e338b5630894a5f779cabb4f9b"},
     {file = "toml-0.10.2.tar.gz", hash = "sha256:b3bda1d108d5dd99f4a20d24d9c348e91c4db7ab1b749200bded2f839ccbe68f"},
 ]
+typed-ast = [
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+]
+typing-extensions = [
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+    {file = "typing_extensions-3.7.4.3.tar.gz", hash = "sha256:99d4073b617d30288f569d3f13d2bd7548c3a7e4c8de87db09a9d29bb3a4a60c"},
+]
 urllib3 = [
     {file = "urllib3-1.26.3-py2.py3-none-any.whl", hash = "sha256:1b465e494e3e0d8939b50680403e3aedaa2bc434b7d5af64dfd3c958d7f5ae80"},
     {file = "urllib3-1.26.3.tar.gz", hash = "sha256:de3eedaad74a2683334e282005cd8d7f22f4d55fa690a2a1020a416cb0a47e73"},
diff --git a/pyproject.toml b/pyproject.toml
index f1d7515..d23ab68 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -12,6 +12,9 @@ lxml = "^4.6.2"
 
 [tool.poetry.dev-dependencies]
 pytest = "^6.2.2"
+black = "^20.8b1"
+flake8 = "^3.9.1"
+isort = "^5.8.0"
 
 [build-system]
 requires = ["poetry-core>=1.0.0"]
@@ -19,3 +22,7 @@ build-backend = "poetry.core.masonry.api"
 
 [tool.poetry.scripts]
 pricehist = "pricehist.cli:cli"
+
+[tool.isort]
+profile = "black"
+multi_line_output = 3