def update_peak_magnitudes(
            self):
        """*update peak magnitudes*

        **Key Arguments:**
            # -

        **Return:**
            - None

        **Usage:**
            ..  todo::

                - add usage info
                - create a sublime snippet for usage
                - write a command-line tool for this method
                - update package tutorial with command-line tool info if needed

            .. code-block:: python

                usage code


        .. todo ::

            - update key arguments values and definitions with defaults
            - update return values and definitions
            - update usage examples and text
            - update docstring text
            - check sublime snippet exists
            - clip any useful text to docs mindmap
            - regenerate the docs and check redendering of this docstring

        """
        self.log.debug('starting the ``update_peak_magnitudes`` method')

        sqlQuery = self.settings["database settings"][
            "transients"]["transient peak magnitude query"]

        sqlQuery = """UPDATE sherlock_crossmatches s,
            (%(sqlQuery)s) t
        SET
            s.transientAbsMag = ROUND(t.mag - IFNULL(direct_distance_modulus,
                            distance_modulus),
                    2)
        WHERE
            IFNULL(direct_distance_modulus,
                    distance_modulus) IS NOT NULL
                AND t.id = s.transient_object_id;""" % locals()

        writequery(
            log=self.log,
            sqlQuery=sqlQuery,
            dbConn=self.transientsDbConn,
        )

        self.log.debug('completed the ``update_peak_magnitudes`` method')
        return None