calculates basic stats on the MapRule elements of the maps
        to give a quick overview.

def get_maps_stats(self):
        """
        calculates basic stats on the MapRule elements of the maps
        to give a quick overview.
        """
        tpes = {}
        for m in self.maps:
            if m.tpe in tpes:
                tpes[m.tpe] += 1
            else:
                tpes[m.tpe] = 1
        return tpes