twitter: use import_source and proper merging for tweets from different sources

+ use proper datetime_aware for created_at

my/twitter/all.py

@@ -1,22 +1,51 @@
 """
 Unified Twitter data (merged from the archive and periodic updates)
 """
+from typing import Iterator
+from ..core import Res
+from ..core.source import import_source
+from .common import merge_tweets, Tweet
+
 
 # NOTE: you can comment out the sources you don't need
-from . import twint, archive
-
-from .common import merge_tweets
+src_twint   = import_source(module_name=f'my.twitter.twint')
+src_archive = import_source(module_name=f'my.twitter.archive')
 
 
-def tweets():
+@src_twint
+def _tweets_twint() -> Iterator[Res[Tweet]]:
+    from . import twint as src
+    return src.tweets()
+
+@src_archive
+def _tweets_archive() -> Iterator[Res[Tweet]]:
+    from . import archive as src
+    return src.tweets()
+
+
+@src_twint
+def _likes_twint() -> Iterator[Res[Tweet]]:
+    from . import twint as src
+    return src.likes()
+
+@src_archive
+def _likes_archive() -> Iterator[Res[Tweet]]:
+    from . import archive as src
+    return src.likes()
+
+
+def tweets() -> Iterator[Res[Tweet]]:
     yield from merge_tweets(
-        twint  .tweets(),
-        archive.tweets(),
+        _tweets_twint(),
+        _tweets_archive(),
     )
 
 
-def likes():
+def likes() -> Iterator[Res[Tweet]]:
     yield from merge_tweets(
-        twint  .likes(),
-        archive.likes(),
+        _likes_twint(),
+        _likes_archive(),
     )
+
+
+# TODO maybe to avoid all the boilerplate above could use some sort of module Protocol?