def could_be_mongo_object_id(test_id:str = "") -> bool:
    """
    Tests if passed-in string is 24 lower-case hexadecimal characters.

    Parameters
    ----------
    test_id : str
        String representing a possible mongodb objectId
    
    Returns
    -------
    test_val : bool
        True if test_id is 24 lower-case hexadecimal characters
    """
    return (len(test_id) == 24
            and all([letter in '0123456789abcdef' for letter in test_id]))