code: def p_cpf_list(self, p):
          '''cpf_list : cpf_list cpf_def
                      | empty'''
          if p[1] is None:
              p[0] = []
          else:
              p[1].append(p[2])
              p[0] = p[1f p_cpf_list(self, p):
          '''cpf_list : cpf_list cpf_def
                      | empty'''
          if p[1] is None:
              p[0] = []
          else:
              p[1].append(p[2])
              p[0] = p[1]
docs: cpf_list : cpf_list cpf_def
                      | empty