mypy fixes

Author: saulshanabrook

pandas/core/frame.py

@@ -8569,13 +8569,13 @@ class _IterableExceptStringOrBytes(metaclass=_IterableExceptStringOrBytesMeta):
     pass
 
 
-@create_block_manager.register
-def _create_block_manager_iterable(
-    data: _IterableExceptStringOrBytes, df, index, columns, dtype, copy
-):
+@create_block_manager.register(_IterableExceptStringOrBytes)
+def _create_block_manager_iterable(data: abc.Iterable, df, index, columns, dtype, copy):
     if not isinstance(data, (abc.Sequence, ExtensionArray)):
         data = list(data)
     if len(data) > 0:
+        # Need this to tell MyPy the proper type
+        data = cast(Union[list, abc.Sequence, ExtensionArray], data)
         if is_dataclass(data[0]):
             data = dataclasses_to_dicts(data)
         if is_list_like(data[0]) and getattr(data[0], "ndim", 1) == 1: