code: def p_type_ref(self, p):
          'type_ref : ID args nullable'
          p[0] = AstTypeRef(
              path=self.path,
              lineno=p.lineno(1),
              lexpos=p.lexpos(1),
              name=p[1],
              args=p[2],
              nullable=p[3],
              ns=None,
          f p_type_ref(self, p):
          'type_ref : ID args nullable'
          p[0] = AstTypeRef(
              path=self.path,
              lineno=p.lineno(1),
              lexpos=p.lexpos(1),
              name=p[1],
              args=p[2],
              nullable=p[3],
              ns=None,
          )
docs: type_ref : ID args nullable