def __len__(self) -> int:
        """
        Gets the number of experiences this stream it's made of.

        :return: The number of experiences in this stream.
        """
        if self.slice_ids is not None:
            return len(self.slice_ids)
        else:
            return self._full_length()

        Gets the number of experiences this stream it's made of.

        :return: The number of experiences in this stream.
        
avalanche/benchmarks/scenarios/generic_scenario.py