Returns the 2 upper ramp points of the main base ramp required for the supply depot and barracks placement properties used in this file.

def upper2_for_ramp_wall(self) -> Set[Point2]:
        """ Returns the 2 upper ramp points of the main base ramp required for the supply depot and barracks placement properties used in this file. """
        if len(self.upper) > 5:
            # NOTE: this was way too slow on large ramps
            return set()  # HACK: makes this work for now
            # FIXME: please do

        upper2 = sorted(list(self.upper), key=lambda x: x.distance_to(self.bottom_center), reverse=True)
        while len(upper2) > 2:
            upper2.pop()
        return set(upper2)