newcol", [99, 99])
        >>> df
           col1  newcol  col2
        0     1      99     3
        1     2      99     4
        >>> df.insert(0, "col1", [100, 100], allow_duplicates=True)
        >>> df
           col1  col1  newcol  col2
        0   100     1      99     3
        1   100     2      99     4

        Notice that pandas uses index alignment in case of `value` from type `Series`:

        >>> df.insert(0, "col0", pd.Series([5, 6], index=[1, 2]))
        >>> df
           col0  col1  col1  newcol  col2
        0   NaN   100     1      99     3
        1   5.0   100     2      99     4
        FzZCannot specify 'allow_duplicates=True' when 'self.flags.allows_duplicate_labels' is False.zcannot insert z