Convert given rollout to Transitions

def to_transitions(self) -> 'Transitions':
        """ Convert given rollout to Transitions """
        # No need to propagate 'rollout_tensors' as they won't mean anything
        return Transitions(
            size=self.num_steps * self.num_envs,
            environment_information=
                [ei for l in self.environment_information for ei in l]
                if self.environment_information is not None else None,
            transition_tensors={
                name: tensor_util.merge_first_two_dims(t) for name, t in self.transition_tensors.items()
            },
            extra_data=self.extra_data
        )