def has_readable_server(self, read_preference=ReadPreference.PRIMARY):
        """Does this topology have any readable servers available matching the
        given read preference?

        :Parameters:
          - `read_preference`: an instance of a read preference from
            :mod:`~pymongo.read_preferences`. Defaults to
            :attr:`~pymongo.read_preferences.ReadPreference.PRIMARY`.

        .. note:: When connected directly to a single server this method
          always returns ``True``.

        .. versionadded:: 3.4
        """
        common.validate_read_preference("read_preference", read_preference)
        return any(self.apply_selector(read_preference, None))
Does this topology have any readable servers available matching the
        given read preference?

        :Parameters:
          - `read_preference`: an instance of a read preference from
            :mod:`~pymongo.read_preferences`. Defaults to
            :attr:`~pymongo.read_preferences.ReadPreference.PRIMARY`.

        .. note:: When connected directly to a single server this method
          always returns ``True``.

        .. versionadded:: 3.4
        
stackoverflow/venv/lib/python3.6/site-packages/pymongo/topology_description.py