    def set_beam_size(self, beam_size):
        """Sets the beam size in the decoder and all children."""
        if getattr(self, "_beam_size", -1) != beam_size:
            seen = set()

            def apply_set_beam_size(module):
                if (
                    module != self
                    and hasattr(module, "set_beam_size")
                    and module not in seen
                ):
                    seen.add(module)
                    module.set_beam_size(beam_size)

            self.apply(apply_set_beam_size)
            self._beam_size = beam_size
Sets the beam size in the decoder and all children.
fairseq/models/fairseq_incremental_decoder.py