DataFrame uses MultiIndex.
    merge_cells : bool, default False
        Format MultiIndex and Hierarchical Rows as merged cells.
    inf_rep : str, default `'inf'`
        representation for np.inf values (which aren't representable in Excel)
        A `'-'` sign will be added in front of -inf.
    style_converter : callable, optional
        This translates Styler styles (CSS) into ExcelWriter styles.
        Defaults to ``CSSToExcelConverter()``.
        It should have signature css_declarations string -> excel style.
        This is only called for body cells.
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