'Called per step of decoding (but only once for dynamic decoding).
Args:
time: Scalar `int32` tensor.
inputs: Input (possibly nested tuple of) tensor[s] for this time step.
state: State (possibly nested tuple of) tensor[s] from previous time step.
name: Name scope for any created operations.
Returns:
`(outputs, next_state, next_inputs, finished)`.'

@abc.abstractmethod
def step(self, time, inputs, state, name=None):

    raise NotImplementedError
