def p_argument_list(self, p):
    ' argument_list :\n                            | expression\n                            | argument_list COMMA expression '
    if (len(p) == 1):
        p[0] = []
    elif (len(p) == 2):
        p[0] = [p[1]]
    else:
        p[0] = p[1]
        p[1].append(p[3])
argument_list :
| expression
| argument_list COMMA expression
def p_argument_list(self, p):
    ' argument_list :\n                            | expression\n                            | argument_list COMMA expression '
    if (len(p) == 1):
        p[0] = []
    elif (len(p) == 2):
        p[0] = [p[1]]
    else:
        p[0] = p[1]
        p[1].append(p[3])