class_docstr: Transformer that predicts blocks of the output in parallel.
code: def _beam_decode(
      self, features, decode_length, beam_size, top_beams, alpha
  ):
      raise NotImplementedError
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from tensor2tensor.data_generators import text_encoder
  from tensor2tensor.layers import common_layers
  from tensor2tensor.models import transformer
  from tensor2tensor.utils import registry
  import tensorflow.compat.v1
  from tensorflow.compat.v1 import estimator
label_desc: Use image node_id 5 for calling the TransformerBlockParallel obj's underlying member method code with example usage: obj._beam_decode(features, decode_length, beam_size, top_beams, alpha) without return types