return True in test_get_required_content_called; do not account for N…

…oneType return in extraction code

datalad_metalad/extract.py

@@ -458,10 +458,9 @@ def perform_dataset_metadata_extraction(ep: ExtractionArguments,
     }
 
     # Let the extractor get the files it requires
-    # Handle both possibilities of bool return and Generator yield
+    # Handle both return possibilities of bool and Generator
     res = extractor.get_required_content()
-
-    if isinstance(res, bool) or res is None:
+    if isinstance(res, bool):
         if res is False:
             yield {
                 "status": "impossible",

datalad_metalad/tests/test_extract.py

@@ -555,6 +555,7 @@ def __init__(self, dataset, ref_commit, parameter):
 
         def get_required_content(self):
             self.required_content_called = True
+            return True
 
         def get_id(self) -> UUID:
             return UUID(int=10)

docs/source/user_guide/writing-extractors.rst

@@ -87,7 +87,7 @@ It will be called by MetaLad prior to metadata extraction.
 Its purpose is to allow the extractor to ensure that content that is required for metadata extraction is present
 (relevant, for example, if some of files to be inspected may be annexed).
 
-The function should either return a boolean value (``True | False``) or yield a ``Generator`` with 
+The function should either return a boolean value (``True | False``) or return a ``Generator`` with 
 `DataLad result records`_. In the case of a boolean value, the function should return ``True`` if
 it has obtained the required content, or confirmed its presence. If it returns ``False``,
 metadata extraction will not proceed. Alternatively, yielding result records provides extractors with