TYP: check_untyped_defs core.internals.concat
pandas\core\internals\concat.py:106: error: Incompatible types in assignment (expression has type "Tuple[Any, ...]", variable has type "List[Any]")  [assignment]
pandas\core\internals\concat.py:131: error: Incompatible types in assignment (expression has type "Tuple[Any, ...]", variable has type "List[Any]")  [assignment]
pandas\core\internals\concat.py:377: error: Need type annotation for 'upcast_classes'  [var-annotated]
pandas\core\internals\concat.py:378: error: Need type annotation for 'null_upcast_classes'  [var-annotated]
LGTM Thanks @simonjayhawkins 