docs: def list_users(contact_points=None, port=None, cql_user=None, cql_pass=None):
      '''
      List existing users in this Cassandra cluster.
  
      :param contact_points: The Cassandra cluster addresses, can either be a string or a list of IPs.
      :type  contact_points: str | list[str]
      :param port:           The Cassandra cluster port, defaults to None.
      :type  port:           int
      :param cql_user:       The Cassandra user if authentication is turned on.
      :type  cql_user:       str
      :param cql_pass:       The Cassandra user password if authentication is turned on.
      :type  cql_pass:       str
      :return:               The list of existing users.
      :rtype:                dict
  
      CLI Example:
  
      .. code-block:: bash
  
          salt 'minion1' cassandra_cql.list_users
  
          salt 'minion1' cassandra_cql.list_users contact_points=minion1
      '''
      query = "list users;"
  
      ret = {}
  
      try:
          ret = cql_query(query, contact_points, port, cql_user, cql_pass)
      except CommandExecutionError:
          log.critical('Could not list users.')
          raise
      except BaseException as e:
          log.critical('Unexpected error while listing users: %s', e)
          raise
  
      return ret