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diff --git a/tensorflow/python/autograph/lang/special_functions.py b/tensorflow/python/autograph/lang/special_functions.py
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+# Copyright 2017 The TensorFlow Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==============================================================================
+"""Special functions that only make sense for AutoGraph.
+
+These functions are meant to ensure feature parity between Python and AutoGraph,
+so that the exact same code works in both modes. In general, AutoGraph will
+replace these calls.
+"""
+
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+
+from tensorflow.python.autograph.operators import data_structures
+
+
+def tensor_list(elements,
+                element_dtype=None,
+                element_shape=None,
+                use_tensor_array=False):
+  """Creates an tensor list and populates it with the given elements.
+
+  This function provides a more uniform access to tensor lists and tensor
+  arrays, and allows optional initialization.
+
+  Note: this function is a simplified wrapper. If you need greater control,
+  it is recommended to use the underlying implementation directly.
+
+  Args:
+    elements: Iterable[tf.Tensor, ...], the elements to initially fill the list
+        with
+    element_dtype: Optional[tf.DType], data type for the elements in the list;
+        required if the list is empty
+    element_shape: Optional[tf.TensorShape], shape for the elements in the list;
+        required if the list is empty
+    use_tensor_array: bool, whether to use the more compatible but restrictive
+        tf.TensorArray implementation
+  Returns:
+    Union[tf.Tensor, tf.TensorArray], the new list.
+  Raises:
+    ValueError: for invalid arguments
+  """
+  if not (elements or (element_dtype and element_shape)):
+    raise ValueError(
+        'element_dtype and element_shape are required for empty lists')
+  if use_tensor_array:
+    return data_structures.tf_tensor_array_new(elements, element_dtype,
+                                               element_shape)
+  else:
+    return data_structures.tf_tensor_list_new(elements, element_dtype,
+                                              element_shape)
+
+
+def stack(list_or_tensor, element_dtype=None, strict=True):
+  """Stacks the input, if it admits the notion of stacking.
+
+  For example, a list of tensors can be stacked into a larger tensor. This
+  function is similar to tf.stack, but it accepts non-lists and lists of
+  non-tensors as arguments. In the latter case, the function does nothing.
+
+  Args:
+    list_or_tensor: Any
+    element_dtype: tf.DType, optional dtypedtype for the elements in the list.
+        Required if the input is stackable, and the list is untyped.
+    strict: bool, if True an error is raised if the input is not stackable.
+        Otherwise the function is a no-op.
+
+  Returns:
+    Any, if the input is stackable, the result will be a tf.Tensor. Otherwise,
+    if strict=False, the result will be list_or_tensor.
+
+  Raises:
+    ValueError: if strict=True and the input is not stackable.
+  """
+  if strict:
+    def raise_error(x):
+      raise ValueError('%s must be stackable when strict=True' % x)
+    original_call = raise_error
+  else:
+    original_call = lambda x: x
+  return data_structures.list_stack(
+      list_or_tensor,
+      data_structures.ListStackOpts(
+          element_dtype=element_dtype, original_call=original_call))