code: def testDenseSequencesToSparse(self):
      labels = [[1, 3, 3, 3, 0], [1, 4, 4, 4, 0], [4, 2, 2, 9, 4]]
      length = [4, 5, 5]
      sparse = ctc_ops.dense_labels_to_sparse(labels, length)
      new_dense = sparse_ops.sparse_tensor_to_dense(sparse)
  
      self.assertAllEqual(labels, new_dense)
  
      padded_labels = [
          [1, 3, 3, 3, 0, 0, 0, 0],
          [1, 4, 4, 4, 0, 0, 0, 0],
          [4, 2, 2, 9, 4, 0, 0, 0],
      ]
      length = [4, 5, 5]
      sparse = ctc_ops.dense_labels_to_sparse(padded_labels, length)
      padded_dense = sparse_ops.sparse_tensor_to_dense(sparse)
  
      self.assertAllEqual(padded_dense, new_dense)
  
imports: from absl.testing import parameterized
  import numpy
  from tensorflow.python.eager import backprop
  from tensorflow.python.eager import context
  from tensorflow.python.eager import def_function
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import errors_impl
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import random_seed
  from tensorflow.python.framework import sparse_tensor
  from tensorflow.python.framework import tensor_spec
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import ctc_ops
  from tensorflow.python.ops import gradients_impl
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import random_ops
  from tensorflow.python.ops import sparse_ops
  from tensorflow.python.platform import test
label_desc: Use image node_id 13 for calling the CTCLossTestV2 obj's underlying member method code with example usage: obj.testDenseSequencesToSparse() without return types