for big_yx in [yx for yx in self.maps if self.maps[yx].modified]:
for y, line in self.maps[big_yx].lines():
write(f, 'MAP_LINE %s %5s %s' % (big_yx, y, quote(line)))
for big_yx in [yx for yx in self.maps if self.maps[yx].modified]:
for y, line in self.maps[big_yx].lines():
write(f, 'MAP_LINE %s %5s %s' % (big_yx, y, quote(line)))