docs: def remove_cache(self, namespace, key=None):
          """Remove all cached values for the specified namespace,
          optionally specifying a key"""
          if key is None:
              self.cursor.execute('DELETE FROM gauged_cache '
                                  'WHERE namespace = %s', (namespace,))
          else:
              self.cursor.execute('DELETE FROM gauged_cache '
                                  'WHERE namespace = %s and `key` = %s',
                                  (namespace, key))