def _get_full_attr_name(attr_name_stack, short_attr_name=None):
    """Join the attr_name_stack to get a full attribute name.

    :param attr_name_stack: List of attribute names sitting on our
        processing stack while building MQL queries.
    :param short_attr_name: The trailing attr_name to be appended to the
        end of our full dot separated attr name.
    :return: A dot separated data key.
    :rtype: str

    """
    return ".".join(
        attr_name_stack + [short_attr_name] if short_attr_name else [])