human: 创建一个注册表单的HTML代码。
 bot: <form>
  <label for="username">用户名:</label><br>
  <input type="text" id="username" name="username"><br>
  <label for="password">密码:</label><br>
  <input type="password" id="password" name="password"><br>
  <label for="email">邮箱:</label><br>
  <input type="email" id="email" name="email"><br>
</form>