def fill(self, background_shape, img):
        """
        Return a proper background image of background_shape, given img.

        Args:
            background_shape (tuple): a shape (h, w)
            img: an image
        Returns:
            a background image
        """
        background_shape = tuple(background_shape)
        return self._fill(background_shape, img)

        Return a proper background image of background_shape, given img.

        Args:
            background_shape (tuple): a shape (h, w)
            img: an image
        Returns:
            a background image
        
tensorpack/dataflow/imgaug/paste.py