class_docstr: Concat CombinerFunction.
class_docstr_tok: ["Concat","CombinerFunction","."]
code: def combine_tensors(self, tensors):
      assert tensors
  
      if len(tensors) == 1:
          return tensors[0]
  
      return tf.concat(tensors, 2)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import abc
  import six
  from tensor2tensor.layers import common_attention
  from tensor2tensor.layers import common_layers
  from tensor2tensor.models import transformer
  from tensor2tensor.models.neural_architecture_search import nas_layers
  from tensor2tensor.utils import contrib
  from tensor2tensor.utils import metrics
  from tensor2tensor.utils import registry
  from tensor2tensor.utils import t2t_model
  import tensorflow.compat.v1
  from tensorflow.compat.v1 import estimator
label_desc: Use image node_id 1 for calling the ConcatCombiner obj's underlying member method code with example usage: obj.combine_tensors(tensors) and returns: tf, tensors