def get_arg_list_value(arg_values, key):
    """
    Check and return an argument value by key.

    Arguments:
        arg_values : list

        key : str

    Returns:
        str
    """

    for item in arg_values:
        if item and item.startswith("{0}=".format(key)):
            return item[(len(key) + 1) :]

    return None