code: def p_definition_list(p):
      
      if len(p) == 3:
          p[0] = p[1] + p[2]
      elif len(p) == 2:
          p[0] = p[1]
      else:
          raise RuntimeError("Invalid production rules 'p_action_list'")
docs: definition_list : definition definition_list
                      | definition