docs: def p_action_precond_section(self, p):
          '''action_precond_section : ACTION_PRECONDITIONS LCURLY action_precond_list RCURLY SEMI
                                    | ACTION_PRECONDITIONS LCURLY RCURLY SEMI'''
          if len(p) == 6:
              p[0] = ('preconds', p[3])
          elif len(p) == 5:
              p[0] = ('preconds', [])
          self._print_verbose('action-preconditions')