core: migrate code to benefit from 3.9 stuff (#401)

for now keeping ruff on 3.8 target version, need to sort out modules as well

my/core/orgmode.py

@@ -1,6 +1,7 @@
 """
 Various helpers for reading org-mode data
 """
+
 from datetime import datetime
 
 
@@ -22,17 +23,20 @@ def parse_org_datetime(s: str) -> datetime:
 
 # TODO I guess want to borrow inspiration from bs4? element type <-> tag; and similar logic for find_one, find_all
 
-from typing import Callable, Iterable, TypeVar
+from collections.abc import Iterable
+from typing import Callable, TypeVar
 
 from orgparse import OrgNode
 
 V = TypeVar('V')
 
+
 def collect(n: OrgNode, cfun: Callable[[OrgNode], Iterable[V]]) -> Iterable[V]:
     yield from cfun(n)
     for c in n.children:
         yield from collect(c, cfun)
 
+
 from more_itertools import one
 from orgparse.extra import Table
 
@@ -46,7 +50,7 @@ class TypedTable(Table):
         tt = super().__new__(TypedTable)
         tt.__dict__ = orig.__dict__
         blocks = list(orig.blocks)
-        header = blocks[0] # fist block is schema
+        header = blocks[0]  # fist block is schema
         if len(header) == 2:
             # TODO later interpret first line as types
             header = header[1:]