code: def get(self, photo_id, width=None, height=None, rect=None):
          
          url = "/photos/%s" % photo_id
          params = {
              "w": width,
              "h": height,
              "rect": rect
          }
          result = self._get(url, params=params)
          return PhotoModel.parse(result)
docs: Retrieve a single photo.
  
          Note: Supplying the optional w or h parameters will result
          in the custom photo URL being added to the 'urls' object:
  
          :param photo_id [string]: The photo’s ID. Required.
          :param width [integer]: Image width in pixels.
          :param height [integer]: Image height in pixels.
          :param rect [string]: 4 comma-separated integers representing x, y, width, height of the cropped rectangle.
          :return: [Photo]: The Unsplash Photo.