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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add(self, obj, metadata=None, update=False):
 """ Add an existing CDSTAR object to the catalog. :param obj: A pycdstar.resource.Object instance """

        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]