docs: def _match_dbname(self, dbname):
          """Map a database name to the Cluster that holds the database.
  
          Args:
              dbname: A database name.
  
          Returns:
              A dict containing the information about the Cluster that holds the
              database.
          """
          for config in self._clusters:
              if re.match(config['pattern'], dbname):
                  return config
          raise Exception('No such database %s.' % dbname)