def update_priorities(self, indices, priorities):
        """
        Update priorities of sampled transitions.
        sets priority of transition at index indices[i] in buffer
        to priorities[i].
        :param indices: [int]
            List of indices of sampled transitions
        :param priorities: [float]
            List of updated priorities corresponding to
            transitions at the sampled indices denoted by
            variable `indices`.
        """
        assert len(indices) == len(priorities)
        for idx, priority in zip(indices, priorities):
            assert priority > 0
            assert 0 <= idx < len(self._storage)
            self._it_sum[idx] = priority ** self._alpha
            self._it_min[idx] = priority ** self._alpha

            self._max_priority = max(self._max_priority, priority)

        Update priorities of sampled transitions.
        sets priority of transition at index indices[i] in buffer
        to priorities[i].
        :param indices: [int]
            List of indices of sampled transitions
        :param priorities: [float]
            List of updated priorities corresponding to
            transitions at the sampled indices denoted by
            variable `indices`.
        
surreal/replay/prioritized_replay.py