    def __len__(self):
        """
        Return the number of entities in the DataCollection.

        Examples:
            >>> from towhee.runtime.data_queue import DataQueue, ColumnType
            >>> from towhee.datacollection.data_collection import DataCollection
            >>> dq = DataQueue([('a', ColumnType.SCALAR), ('b', ColumnType.QUEUE)])
            >>> dc = DataCollection(dq)
            >>> len(dc)
            0
        """
        return len(self._iterable)
Return the number of entities in the DataCollection.

Examples:
>>> from towhee.runtime.data_queue import DataQueue, ColumnType
>>> from towhee.datacollection.data_collection import DataCollection
>>> dq = DataQueue([('a', ColumnType.SCALAR), ('b', ColumnType.QUEUE)])
>>> dc = DataCollection(dq)
>>> len(dc)
0
towhee/datacollection/data_collection.py