code: def p_subidentifiers_defval(self, p):
          
          n = len(p)
          if n == 3:
              p[0] = ('subidentifiers_defval', p[1][1] + [p[2]])
          elif n == 2:
              p[0] = ('subidentifiers_defval', [p[1]])
docs: subidentifiers_defval : subidentifiers_defval subidentifier_defval
                                   | subidentifier_defval