code: def testFlattenDataclass(self):
      mt = MaskedTensor(mask=True, value=constant_op.constant([1]))
      leaves = nest.flatten(mt)
      self.assertLen(leaves, 1)
      self.assertAllEqual(leaves[0], [1])
  
imports: import collections
  import dataclasses
  from absl.testing import parameterized
  import numpy
  from tensorflow.python.data.kernel_tests import test_base
  from tensorflow.python.data.util import nest
  from tensorflow.python.framework import combinations
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import sparse_tensor
  from tensorflow.python.framework import tensor
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops.ragged import ragged_factory_ops
  from tensorflow.python.platform import test
label_desc: Use image node_id 3 for calling the NestTest obj's underlying member method code with example usage: obj.testFlattenDataclass() without return types