Retrieves a url for the photo.  (flickr.photos.getSizes)

        urlType - 'url' or 'source'
        'url' - flickr page of photo
        'source' - image file

def getURL(self, size='Medium', urlType='url'):
        """Retrieves a url for the photo.  (flickr.photos.getSizes)

        urlType - 'url' or 'source'
        'url' - flickr page of photo
        'source' - image file
        """
        method = 'flickr.photos.getSizes'
        data = _doget(method, photo_id=self.id)
        for psize in data.rsp.sizes.size:
            if psize.label == size:
                return getattr(psize, urlType)
        raise FlickrError, "No URL found"