Return the information if a mapping exists.

    :param kb_name: knowledge base name
    :param key: left side (mapFrom)

def kb_mapping_exists(kb_name, key):
    """Return the information if a mapping exists.

    :param kb_name: knowledge base name
    :param key: left side (mapFrom)
    """
    try:
        kb = get_kb_by_name(kb_name)
    except NoResultFound:
        return False
    return key in kb.kbrvals