TYP: type error in `pandas/io/excel/_xlsxwriter.py`

[fangchenli]

Those are some of the typing errors generated by mypy after unpining it.

pandas/io/excel/_xlsxwriter.py:105: error: "object" has no attribute "__iter__"; maybe "__str__" or "__dir__"? (not iterable)  [attr-defined]
pandas/io/excel/_xlsxwriter.py:196: error: "None" has no attribute "close"  [attr-defined]
pandas/io/excel/_xlsxwriter.py:207: error: "None" has no attribute "add_worksheet"  [attr-defined]
pandas/io/excel/_xlsxwriter.py:225: error: "None" has no attribute "add_format"  [attr-defined]