def testMixedTensorAndIndexedSlices(self):
   t0 = math_ops._as_indexed_slices(constant_op.constant(
       [[1., 2.], [0, 0], [3., 4.]]))
   t1 = constant_op.constant(
       [[0., 0.], [5, 6], [7., 8.]])
   total = constant_op.constant(
       [[1., 2.], [5, 6], [10., 12.]])
   result = gradients_impl._AggregateIndexedSlicesGradients([t0, t1])
   self._assert_indexed_slices_equal(total, result)

 def testMultipleGradientsWithNones(self):
   t0 = math_ops._as_indexed_slices(constant_op.constant(
       [[1., 2.], [0, 0], [3., 4.]]))
   t1 = math_ops._as_indexed_slices(constant_op.constant(
       [[0., 0.], [5, 6], [7., 8.]]))
   t3 = None
   total = constant_op.constant(
       [[1., 2.], [5, 6], [10., 12.]])
   result = gradients_impl._AggregateIndexedSlicesGradients([t0, t1, t3])
   self._assert_indexed_slices_equal(total, result)

def aggregate_tensors_or_indexed_slices(values, accumulation_fn=math_ops.add_n):
  """Aggregate tensors using `accumulation_fn` and IndexedSlices via concat."""
  if any(isinstance(v, ops.IndexedSlices) for v in values):
    return gradients_impl._AggregateIndexedSlicesGradients(values)  # pylint: disable=protected-access
  else:
    return accumulation_fn(values)

 def testOneGradient(self):
   t = math_ops._as_indexed_slices(constant_op.constant(
       [[1., 2.], [0, 0], [3., 4.]]))
   result = gradients_impl._AggregateIndexedSlicesGradients([t])
   self._assert_indexed_slices_equal(t, result)

 def testNoGradients(self):
   self.assertIsNone(gradients_impl._AggregateIndexedSlicesGradients([]))