    def _inc_lat(self, latitude, delta):
        """Shift the latitude by the required number of pixels (i.e. text lines)."""
        y = self._convert_latitude(latitude)
        y += delta
        return 360 / pi * atan(
            exp((180 - y * 360 / (2 ** self._zoom) / self._size) * pi / 180)) - 90
Shift the latitude by the required number of pixels (i.e. text lines).
samples/maps.py