code: def p_portlist_empty(self, p):
          'portlist : SEMICOLON'
          p[0] = Portlist(ports=(), lineno=p.lineno(1))
          p.set_lineno(0, p.lineno(1)f p_portlist_empty(self, p):
          'portlist : SEMICOLON'
          p[0] = Portlist(ports=(), lineno=p.lineno(1))
          p.set_lineno(0, p.lineno(1))
docs: portlist : SEMICOLON