docs: def get_instance_from_id(unique_id):
          """Get an instance of the `PolygonFilter` using a unique id"""
          for instance in PolygonFilter.instances:
              if instance.unique_id == unique_id:
                  return instance
          # if this does not work:
          raise KeyError("PolygonFilter with unique_id {} not found.".
                         format(unique_id))