@staticmethod
def p_xcp_on_can_optional_list(p):
    """xcp_on_can_optional_list : xcp_on_can_optional
                                    | xcp_on_can_optional xcp_on_can_optional_list"""
    try:
        p[0] = [p[1]] + p[2]
    except IndexError:
        p[0] = [p[1]]
