docs: def master_tops(self):
          '''
          Return the metadata derived from the master_tops system
          '''
          log.debug(
              'The _ext_nodes master function has been renamed to _master_tops. '
              'To ensure compatibility when using older Salt masters we will '
              'continue to invoke the function as _ext_nodes until the '
              'Magnesium release.'
          )
          # TODO: Change back to _master_tops
          # for Magnesium release
          load = {'cmd': '_ext_nodes',
                  'id': self.opts['id'],
                  'opts': self.opts}
          if self.auth:
              load['tok'] = self.auth.gen_token(b'salt')
          return salt.utils.data.decode(self.channel.send(load)) if six.PY2 \
              else self.channel.send(load)