TYP: misc typing cleanup in core/indexes/multi.py
pandas\core\indexes\multi.py:496: error: Need type annotation for 'arrays'  [var-annotated]
pandas\core\indexes\multi.py:722: error: Incompatible types in assignment (expression has type "List[Any]", variable has type "FrozenList")  [assignment]
pandas\core\indexes\multi.py:893: error: Incompatible types in assignment (expression has type "List[Any]", variable has type "FrozenList")  [assignment]
pandas\core\indexes\multi.py:2438: error: List item 0 has incompatible type "slice"; expected "str"  [list-item]
pandas\core\indexes\multi.py:3095: error: Unsupported left operand type for | ("None")  [operator]
thanks @simonjayhawkins 