code: def like(self, photo_id):
          
          url = "/photos/%s/like" % photo_id
          result = self._post(url)
          return PhotoModel.parse(result)
docs: Like a photo on behalf of the logged-in user.
          This requires the 'write_likes' scope.
  
          Note: This action is idempotent; sending the POST request
          to a single photo multiple times has no additional effect.
  
          :param photo_id [string]: The photo’s ID. Required.
          :return: [Photo]: The Unsplash Photo.