Vel factory function

def create(replay_buffer, discount_factor: typing.Optional[float]=None, normalize_returns: bool=False,
           forward_steps: int=1, action_noise: typing.Optional[ModelFactory]=None):
    """ Vel factory function """
    return TransitionReplayEnvRollerFactory(
        replay_buffer_factory=replay_buffer,
        discount_factor=discount_factor,
        forward_steps=forward_steps,
        normalize_returns=normalize_returns,
        action_noise=action_noise
    )