Remove some dead code after migration from python to C.

PiperOrigin-RevId: 213372027

2 files changed, 3 insertions, 21 deletions

diff --git a/tensorflow/python/eager/backprop.py b/tensorflow/python/eager/backprop.py
index e6cf9653a8..907234b0f8 100644
--- a/tensorflow/python/eager/backprop.py
+++ b/tensorflow/python/eager/backprop.py
@@ -120,27 +120,6 @@ def _gradient_function(op_name, attr_tuple, num_inputs, inputs, outputs,
 pywrap_tensorflow.TFE_Py_RegisterGradientFunction(_gradient_function)
 
 
-_tracing = False
-
-
-# TODO(agarwal): use an automatic mechanism for handling None arguments to
-# gradient functions.
-# Some gradient functions can accept None arguments for gradients. The following
-# maps the operation name to the indices at which the corresponding gradient
-# function can accept None values.
-# e.g. FusedBatchNorm outputs 5 values and hence receives 5 gradient values
-# during backprop. However the gradient function uses only the first of those
-# values and ignores the rest. The entry, "FusedBatchNorm": [1, 2, 3, 4],
-# indicates that only the gradient corresponding to index 0 is used, and the
-# gradient values at indices 1-4 are ignored (and hence can be None). The
-# backprop algorithm can then leverage this by not constructing zeros to
-# pass for those indices.
-_grad_fn_accepts_none_for_indices = {
-    "SoftmaxCrossEntropyWithLogits": [1],
-    "FusedBatchNorm": [1, 2, 3, 4]
-}
-
-
 def _record_gradient(op_name, inputs, attrs, results, name):
   return pywrap_tensorflow.TFE_Py_RecordGradient(op_name, inputs, attrs,
                                                  results, name)
diff --git a/tensorflow/python/eager/pywrap_tfe_src.cc b/tensorflow/python/eager/pywrap_tfe_src.cc
index 9f2f4e06ad..99b46159a9 100644
--- a/tensorflow/python/eager/pywrap_tfe_src.cc
+++ b/tensorflow/python/eager/pywrap_tfe_src.cc
@@ -1744,6 +1744,9 @@ PyObject* MaybeGetDTypeForAttr(const string& attr,
   Py_RETURN_NONE;
 }
 
+// TODO(agarwal): use an automatic mechanism for handling None arguments to
+// gradient functions.
+
 // Returns a pair where the first value of the pair indicates whether or not all
 // outputs are unused. If the first value is false, the second value is a
 // set that identifies which of the output indices are unused.