use append for single elements, extend doesn't work
@@ -359,7 +359,7 @@ class GeometryChangeTracker:
self.finalize()
other.finalize()
for level_id in other._geometries_by_level.keys():
- self._geometries_by_level.setdefault(level_id, []).extend(self._get_unary_union(level_id))
+ self._geometries_by_level.setdefault(level_id, []).append(self._get_unary_union(level_id))
self._unary_unions = {}
def save(self, last_update, new_update):
