Localize tz-naive Datetime Array/Index to tz-aware
        Datetime Array/Index.

        This method takes a time zone (tz) naive Datetime Array/Index object
        and makes this time zone aware. It does not move the time to another
        time zone.
        Time zone localization helps to switch from time zone aware to time
        zone unaware objects.

        Parameters
        ----------
        tz : str, pytz.timezone, dateutil.tz.tzfile or None
            Time zone to convert timestamps to. Passing ``None`` will
            remove the time zone information preserving local time.
        ambiguous : 'infer', 'NaT', bool array, default 'raise'
            When clocks moved backward due to DST, ambiguous times may arise.
            For example in Central European Time (UTC+01), when going from
            03:00 DST to 02:00 non-DST, 02:30:00 local time occurs both at
            00:30:00 UTC and at 01:30:00 UTC. In such a situation, the
            `ambiguous` parameter dictates how ambiguous times should be
            handled.

            - 'infer' will attempt to infer fall dst-transition hours based on
              order
            - bool-ndarray where True signifies a DST time, False signifies a
              non-DST time (note that this flag is only applicable for
              ambiguous times)
            - 'NaT' will return NaT where there are ambiguous times
            - 'raise' will raise an AmbiguousTimeError if there are ambiguous
              times

        nonexistent : 'shift_forward', 'shift_backward, 'NaT', timedelta, \
default 'raise'
            A nonexistent time does not exist in a particular timezone
            where clocks moved forward due to DST.

            - 'shift_forward' will shift the nonexistent time forward to the
              closest existing time
            - 'shift_backward' will shift the nonexistent time backward to the
              closest existing time
            - 'NaT' will return NaT where there are nonexistent times
            - timedelta objects will shift nonexistent times by the timedelta
            - 'raise' will raise an NonExistentTimeError if there are
              nonexistent times

            .. versionadded:: 0.24.0

        errors : {'raise', 'coerce'}, default None

            - 'raise' will raise a NonExistentTimeError if a timestamp is not
              valid in the specified time zone (e.g. due to a transition from
              or to DST time). Use ``nonexistent='raise'`` instead.
            - 'coerce' will return NaT if the timestamp can not be converted
              to the specified time zone. Use ``nonexistent='NaT'`` instead.

            .. deprecated:: 0.24.0

        Returns
        -------
        Same type as self
            Array/Index converted to the specified time zone.

        Raises
        ------
        TypeError
            If the Datetime Array/Index is tz-aware and tz is not None.

        See Also
        --------
        DatetimeIndex.tz_convert : Convert tz-aware DatetimeIndex from
            one time zone to another.

        Examples
        --------
        >>> tz_naive = pd.date_range('2018-03-01 09:00', periods=3)
        >>> tz_naive
        DatetimeIndex(['2018-03-01 09:00:00', '2018-03-02 09:00:00',
                       '2018-03-03 09:00:00'],
                      dtype='datetime64[ns]', freq='D')

        Localize DatetimeIndex in US/Eastern time zone:

        >>> tz_aware = tz_naive.tz_localize(tz='US/Eastern')
        >>> tz_aware
        DatetimeIndex(['2018-03-01 09:00:00-05:00',
                       '2018-03-02 09:00:00-05:00',
                       '2018-03-03 09:00:00-05:00'],
                      dtype='datetime64[ns, US/Eastern]', freq='D')

        With the ``tz=None``, we can remove the time zone information
        while keeping the local time (not converted to UTC):

        >>> tz_aware.tz_localize(None)
        DatetimeIndex(['2018-03-01 09:00:00', '2018-03-02 09:00:00',
                       '2018-03-03 09:00:00'],
                      dtype='datetime64[ns]', freq='D')

        Be careful with DST changes. When there is sequential data, pandas can
        infer the DST time:
        >>> s = pd.to_datetime(pd.Series(['2018-10-28 01:30:00',
        ...                               '2018-10-28 02:00:00',
        ...                               '2018-10-28 02:30:00',
        ...                               '2018-10-28 02:00:00',
        ...                               '2018-10-28 02:30:00',
        ...                               '2018-10-28 03:00:00',
        ...                               '2018-10-28 03:30:00']))
        >>> s.dt.tz_localize('CET', ambiguous='infer')
        0   2018-10-28 01:30:00+02:00
        1   2018-10-28 02:00:00+02:00
        2   2018-10-28 02:30:00+02:00
        3   2018-10-28 02:00:00+01:00
        4   2018-10-28 02:30:00+01:00
        5   2018-10-28 03:00:00+01:00
        6   2018-10-28 03:30:00+01:00
        dtype: datetime64[ns, CET]

        In some cases, inferring the DST is impossible. In such cases, you can
        pass an ndarray to the ambiguous parameter to set the DST explicitly

        >>> s = pd.to_datetime(pd.Series(['2018-10-28 01:20:00',
        ...                               '2018-10-28 02:36:00',
        ...                               '2018-10-28 03:46:00']))
        >>> s.dt.tz_localize('CET', ambiguous=np.array([True, True, False]))
        0   2015-03-29 03:00:00+02:00
        1   2015-03-29 03:30:00+02:00
        dtype: datetime64[ns, Europe/Warsaw]

        If the DST transition causes nonexistent times, you can shift these
        dates forward or backwards with a timedelta object or `'shift_forward'`
        or `'shift_backwards'`.
        >>> s = pd.to_datetime(pd.Series(['2015-03-29 02:30:00',
        ...                               '2015-03-29 03:30:00']))
        >>> s.dt.tz_localize('Europe/Warsaw', nonexistent='shift_forward')
        0   2015-03-29 03:00:00+02:00
        1   2015-03-29 03:30:00+02:00
        dtype: datetime64[ns, 'Europe/Warsaw']
        >>> s.dt.tz_localize('Europe/Warsaw', nonexistent='shift_backward')
        0   2015-03-29 01:59:59.999999999+01:00
        1   2015-03-29 03:30:00+02:00
        dtype: datetime64[ns, 'Europe/Warsaw']
        >>> s.dt.tz_localize('Europe/Warsaw', nonexistent=pd.Timedelta('1H'))
        0   2015-03-29 03:30:00+02:00
        1   2015-03-29 03:30:00+02:00
        dtype: datetime64[ns, 'Europe/Warsaw']

def tz_localize(self, tz, ambiguous='raise', nonexistent='raise',
                    errors=None):
        """
        Localize tz-naive Datetime Array/Index to tz-aware
        Datetime Array/Index.

        This method takes a time zone (tz) naive Datetime Array/Index object
        and makes this time zone aware. It does not move the time to another
        time zone.
        Time zone localization helps to switch from time zone aware to time
        zone unaware objects.

        Parameters
        ----------
        tz : str, pytz.timezone, dateutil.tz.tzfile or None
            Time zone to convert timestamps to. Passing ``None`` will
            remove the time zone information preserving local time.
        ambiguous : 'infer', 'NaT', bool array, default 'raise'
            When clocks moved backward due to DST, ambiguous times may arise.
            For example in Central European Time (UTC+01), when going from
            03:00 DST to 02:00 non-DST, 02:30:00 local time occurs both at
            00:30:00 UTC and at 01:30:00 UTC. In such a situation, the
            `ambiguous` parameter dictates how ambiguous times should be
            handled.

            - 'infer' will attempt to infer fall dst-transition hours based on
              order
            - bool-ndarray where True signifies a DST time, False signifies a
              non-DST time (note that this flag is only applicable for
              ambiguous times)
            - 'NaT' will return NaT where there are ambiguous times
            - 'raise' will raise an AmbiguousTimeError if there are ambiguous
              times

        nonexistent : 'shift_forward', 'shift_backward, 'NaT', timedelta, \
default 'raise'
            A nonexistent time does not exist in a particular timezone
            where clocks moved forward due to DST.

            - 'shift_forward' will shift the nonexistent time forward to the
              closest existing time
            - 'shift_backward' will shift the nonexistent time backward to the
              closest existing time
            - 'NaT' will return NaT where there are nonexistent times
            - timedelta objects will shift nonexistent times by the timedelta
            - 'raise' will raise an NonExistentTimeError if there are
              nonexistent times

            .. versionadded:: 0.24.0

        errors : {'raise', 'coerce'}, default None

            - 'raise' will raise a NonExistentTimeError if a timestamp is not
              valid in the specified time zone (e.g. due to a transition from
              or to DST time). Use ``nonexistent='raise'`` instead.
            - 'coerce' will return NaT if the timestamp can not be converted
              to the specified time zone. Use ``nonexistent='NaT'`` instead.

            .. deprecated:: 0.24.0

        Returns
        -------
        Same type as self
            Array/Index converted to the specified time zone.

        Raises
        ------
        TypeError
            If the Datetime Array/Index is tz-aware and tz is not None.

        See Also
        --------
        DatetimeIndex.tz_convert : Convert tz-aware DatetimeIndex from
            one time zone to another.

        Examples
        --------
        >>> tz_naive = pd.date_range('2018-03-01 09:00', periods=3)
        >>> tz_naive
        DatetimeIndex(['2018-03-01 09:00:00', '2018-03-02 09:00:00',
                       '2018-03-03 09:00:00'],
                      dtype='datetime64[ns]', freq='D')

        Localize DatetimeIndex in US/Eastern time zone:

        >>> tz_aware = tz_naive.tz_localize(tz='US/Eastern')
        >>> tz_aware
        DatetimeIndex(['2018-03-01 09:00:00-05:00',
                       '2018-03-02 09:00:00-05:00',
                       '2018-03-03 09:00:00-05:00'],
                      dtype='datetime64[ns, US/Eastern]', freq='D')

        With the ``tz=None``, we can remove the time zone information
        while keeping the local time (not converted to UTC):

        >>> tz_aware.tz_localize(None)
        DatetimeIndex(['2018-03-01 09:00:00', '2018-03-02 09:00:00',
                       '2018-03-03 09:00:00'],
                      dtype='datetime64[ns]', freq='D')

        Be careful with DST changes. When there is sequential data, pandas can
        infer the DST time:
        >>> s = pd.to_datetime(pd.Series(['2018-10-28 01:30:00',
        ...                               '2018-10-28 02:00:00',
        ...                               '2018-10-28 02:30:00',
        ...                               '2018-10-28 02:00:00',
        ...                               '2018-10-28 02:30:00',
        ...                               '2018-10-28 03:00:00',
        ...                               '2018-10-28 03:30:00']))
        >>> s.dt.tz_localize('CET', ambiguous='infer')
        0   2018-10-28 01:30:00+02:00
        1   2018-10-28 02:00:00+02:00
        2   2018-10-28 02:30:00+02:00
        3   2018-10-28 02:00:00+01:00
        4   2018-10-28 02:30:00+01:00
        5   2018-10-28 03:00:00+01:00
        6   2018-10-28 03:30:00+01:00
        dtype: datetime64[ns, CET]

        In some cases, inferring the DST is impossible. In such cases, you can
        pass an ndarray to the ambiguous parameter to set the DST explicitly

        >>> s = pd.to_datetime(pd.Series(['2018-10-28 01:20:00',
        ...                               '2018-10-28 02:36:00',
        ...                               '2018-10-28 03:46:00']))
        >>> s.dt.tz_localize('CET', ambiguous=np.array([True, True, False]))
        0   2015-03-29 03:00:00+02:00
        1   2015-03-29 03:30:00+02:00
        dtype: datetime64[ns, Europe/Warsaw]

        If the DST transition causes nonexistent times, you can shift these
        dates forward or backwards with a timedelta object or `'shift_forward'`
        or `'shift_backwards'`.
        >>> s = pd.to_datetime(pd.Series(['2015-03-29 02:30:00',
        ...                               '2015-03-29 03:30:00']))
        >>> s.dt.tz_localize('Europe/Warsaw', nonexistent='shift_forward')
        0   2015-03-29 03:00:00+02:00
        1   2015-03-29 03:30:00+02:00
        dtype: datetime64[ns, 'Europe/Warsaw']
        >>> s.dt.tz_localize('Europe/Warsaw', nonexistent='shift_backward')
        0   2015-03-29 01:59:59.999999999+01:00
        1   2015-03-29 03:30:00+02:00
        dtype: datetime64[ns, 'Europe/Warsaw']
        >>> s.dt.tz_localize('Europe/Warsaw', nonexistent=pd.Timedelta('1H'))
        0   2015-03-29 03:30:00+02:00
        1   2015-03-29 03:30:00+02:00
        dtype: datetime64[ns, 'Europe/Warsaw']
        """
        if errors is not None:
            warnings.warn("The errors argument is deprecated and will be "
                          "removed in a future release. Use "
                          "nonexistent='NaT' or nonexistent='raise' "
                          "instead.", FutureWarning)
            if errors == 'coerce':
                nonexistent = 'NaT'
            elif errors == 'raise':
                nonexistent = 'raise'
            else:
                raise ValueError("The errors argument must be either 'coerce' "
                                 "or 'raise'.")

        nonexistent_options = ('raise', 'NaT', 'shift_forward',
                               'shift_backward')
        if nonexistent not in nonexistent_options and not isinstance(
                nonexistent, timedelta):
            raise ValueError("The nonexistent argument must be one of 'raise',"
                             " 'NaT', 'shift_forward', 'shift_backward' or"
                             " a timedelta object")

        if self.tz is not None:
            if tz is None:
                new_dates = tzconversion.tz_convert(self.asi8, timezones.UTC,
                                                    self.tz)
            else:
                raise TypeError("Already tz-aware, use tz_convert to convert.")
        else:
            tz = timezones.maybe_get_tz(tz)
            # Convert to UTC

            new_dates = conversion.tz_localize_to_utc(
                self.asi8, tz, ambiguous=ambiguous, nonexistent=nonexistent,
            )
        new_dates = new_dates.view(_NS_DTYPE)
        dtype = tz_to_dtype(tz)
        return self._simple_new(new_dates, dtype=dtype, freq=self.freq)