def _check_agent_id(agent_id):
    """Checks that the given agent_id is a valid non-empty string.

    :param str agent_id: agent id to check.

    :raise CraftAiBadRequestError: If the given agent_id is not of
    type string or if it is an empty string.
    """
    if (not isinstance(agent_id, six.string_types) or
        AGENT_ID_PATTERN.match(agent_id) is None):
      raise CraftAiBadRequestError(ERROR_ID_MESSAGE)
Checks that the given agent_id is a valid non-empty string.

    :param str agent_id: agent id to check.

    :raise CraftAiBadRequestError: If the given agent_id is not of
    type string or if it is an empty string.