Method ExtendStep

Transformer Layer, extend one step in decoding. This function is expected to be called during fast decoding of Transformer models. Args: theta: A `.NestedMap` object containing weights' values of this layer and its children layers. source_vecs: [source_batch, dim].

(self,
                 theta,
                 source_vecs,
                 prefix_states,
                 aux_vecs=None,
                 aux_paddings=None,
                 t=None,
                 **kwargs)