docs: def p_action_precond_list(self, p):
          '''action_precond_list : action_precond_list action_precond_def
                                 | action_precond_def'''
          if len(p) == 3:
              p[1].append(p[2])
              p[0] = p[1]
          elif len(p) == 2:
              p[0] = [p[1]]