def get_region_size(region):
        """ Finds and returns the approximate size of region (in degrees)  
        from a HEALPix region string.   
        """
        if region is None:
            return 180.
        tokens = parse_hpxregion(region)
        if tokens[0] in ['DISK', 'DISK_INC']:
            return float(tokens[3])
        elif tokens[0] == 'HPX_PIXEL':
            pixel_size = get_pixel_size_from_nside(int(tokens[2]))
            return 2. * pixel_size
        else:
            raise Exception(
                "HPX.get_region_size did not recognize region type %s" % tokens[0])
        return None
Finds and returns the approximate size of region (in degrees)  
        from a HEALPix region string.