Copy the query and add filtering by metric labels.

        Examples::

            query = query.select_metrics(instance_name='myinstance')
            query = query.select_metrics(instance_name_prefix='mycluster-')

        A keyword argument ``<label>=<value>`` ordinarily generates a filter
        expression of the form::

            metric.label.<label> = "<value>"

        However, by adding ``"_prefix"`` or ``"_suffix"`` to the keyword,
        you can specify a partial match.

        ``<label>_prefix=<value>`` generates::

            metric.label.<label> = starts_with("<value>")

        ``<label>_suffix=<value>`` generates::

            metric.label.<label> = ends_with("<value>")

        If the label's value type is ``INT64``, a similar notation can be
        used to express inequalities:

        ``<label>_less=<value>`` generates::

            metric.label.<label> < <value>

        ``<label>_lessequal=<value>`` generates::

            metric.label.<label> <= <value>

        ``<label>_greater=<value>`` generates::

            metric.label.<label> > <value>

        ``<label>_greaterequal=<value>`` generates::

            metric.label.<label> >= <value>

        :type args: tuple
        :param args: Raw filter expression strings to include in the
            conjunction. If just one is provided and no keyword arguments
            are provided, it can be a disjunction.

        :type kwargs: dict
        :param kwargs: Label filters to include in the conjunction as
            described above.

        :rtype: :class:`Query`
        :returns: The new query object.

def select_metrics(self, *args, **kwargs):
        """Copy the query and add filtering by metric labels.

        Examples::

            query = query.select_metrics(instance_name='myinstance')
            query = query.select_metrics(instance_name_prefix='mycluster-')

        A keyword argument ``<label>=<value>`` ordinarily generates a filter
        expression of the form::

            metric.label.<label> = "<value>"

        However, by adding ``"_prefix"`` or ``"_suffix"`` to the keyword,
        you can specify a partial match.

        ``<label>_prefix=<value>`` generates::

            metric.label.<label> = starts_with("<value>")

        ``<label>_suffix=<value>`` generates::

            metric.label.<label> = ends_with("<value>")

        If the label's value type is ``INT64``, a similar notation can be
        used to express inequalities:

        ``<label>_less=<value>`` generates::

            metric.label.<label> < <value>

        ``<label>_lessequal=<value>`` generates::

            metric.label.<label> <= <value>

        ``<label>_greater=<value>`` generates::

            metric.label.<label> > <value>

        ``<label>_greaterequal=<value>`` generates::

            metric.label.<label> >= <value>

        :type args: tuple
        :param args: Raw filter expression strings to include in the
            conjunction. If just one is provided and no keyword arguments
            are provided, it can be a disjunction.

        :type kwargs: dict
        :param kwargs: Label filters to include in the conjunction as
            described above.

        :rtype: :class:`Query`
        :returns: The new query object.
        """
        new_query = copy.deepcopy(self)
        new_query._filter.select_metrics(*args, **kwargs)
        return new_query