'Constructs LM graph from inputs to LM loss.
* Caches the VatxtInput object in `self.lm_inputs`
* Caches tensors: `lm_embedded`
Args:
compute_loss: bool, whether to compute and return the loss or stop after
the LSTM computation.
Returns:
loss: scalar float.'

def language_model_graph(self, compute_loss=True):

    inputs = _inputs('train', pretrain=True)
    self.lm_inputs = inputs
    return self._lm_loss(inputs, compute_loss=compute_loss)
