text: Title: [BUG]description for query paramters can not show in swagger ui
  Body: Hi, when I add a description for a schema used in query, it can not show in swagger ui but can show in Redoc
  ```py
  @HELLO.route('/', methods=['GET'])
  @api.validate(query=HelloForm)
  def hello():
      """
      hello 注释
      :return:
      """
     return 'ok'
  
  class HelloForm(BaseModel):
      """
      hello表单
      """
      user: str # 用户名称
      msg: str = Field(description='msg test', example='aa')
      index: int
      data: HelloGetListForm
      list: List[HelloListForm]
  ```
  
  ![截屏2020-10-12 下午7 54 52](https://user-images.githubusercontent.com/60063723/95743785-de70f480-0cc4-11eb-857b-fffd3d7e9cdd.png)
  ![截屏2020-10-12 下午7 53 59](https://user-images.githubusercontent.com/60063723/95743805-e5980280-0cc4-11eb-99ae-11e6439bae02.png)
  
  
  