code: def add(self, obj, metadata=None, update=False):
          
          if (obj not in self) or update:
              self[obj.id] = Object.fromdict(
                  obj.id,
                  dict(
                      metadata=obj.metadata.read() if metadata is None else metadata,
                      bitstreams=[bs._properties for bs in obj.bitstreams]))
              time.sleep(0.1)
              return self.objects[obj.id]
docs: Add an existing CDSTAR object to the catalog.
  
          :param obj: A pycdstar.resource.Object instance