Also make a copy of the underlying data.

        Returns
        -------
        {klass}
            Object with time zone converted axis.

        Raises
        ------
        TypeError
            If the axis is tz-naive.

        Examples
        --------
        Change to another time zone:

        >>> s = pd.Series(
        ...     [1],
        ...     index=pd.DatetimeIndex(['2018-09-15 01:30:00+02:00']),
        ... )
        >>> s.tz_convert('Asia/Shanghai')
        2018-09-15 07:30:00+08:00    1
        dtype: int64

        Pass None to convert to UTC and get a tz-naive index:

        >>> s = pd.Series([1],
        ...     index=pd.DatetimeIndex(['2018-09-15 01:30:00+02:00']))
        >>> s.tz_convert(None)
        2018-09-14 23:30:00    1
        dtype: int64
        c