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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get(self, photo_id, width=None, height=None, rect=None):
 """ 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. """

        url = "/photos/%s" % photo_id
        params = {
            "w": width,
            "h": height,
            "rect": rect
        }
        result = self._get(url, params=params)
        return PhotoModel.parse(result)