From 509898b471efdd7c66b3d5b8edc7e3b5be4adb6f Mon Sep 17 00:00:00 2001
From: Mustafa Ispir <ispir@google.com>
Date: Thu, 2 Mar 2017 16:15:48 -0800
Subject: Error out if a subclass of Estimator overrides a member of Estimator.
 Change: 149060568

---
 tensorflow/python/estimator/estimator.py      | 17 +++++++++++++-
 tensorflow/python/estimator/estimator_test.py | 32 +++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/tensorflow/python/estimator/estimator.py b/tensorflow/python/estimator/estimator.py
index 5d4472556c..a52d3fb2e0 100644
--- a/tensorflow/python/estimator/estimator.py
+++ b/tensorflow/python/estimator/estimator.py
@@ -70,7 +70,7 @@ class Estimator(object):
   inspect it. The structure of params is therefore entirely up to the developer.
   """
 
-  def __init__(self, model_fn=None, model_dir=None, config=None, params=None):
+  def __init__(self, model_fn, model_dir=None, config=None, params=None):
     """Constructs an `Estimator` instance.
 
     Args:
@@ -109,7 +109,10 @@ class Estimator(object):
 
     Raises:
       ValueError: parameters of `model_fn` don't match `params`.
+      ValueError: if this is called via a subclass and if that class overrides
+        a member of `Estimator`.
     """
+    self._assert_members_are_not_overridden()
     # Model directory.
     self._model_dir = model_dir
     if self._model_dir is None:
@@ -312,6 +315,18 @@ class Estimator(object):
                   for key, value in six.iteritems(preds_evaluated)
               }
 
+  def _assert_members_are_not_overridden(self):
+    estimator_members = set([m for m in Estimator.__dict__.keys()
+                             if not m.startswith('__')])
+    subclass_members = set(self.__class__.__dict__.keys())
+    common_members = estimator_members & subclass_members
+    overriden_members = [m for m in common_members
+                         if Estimator.__dict__[m] != self.__class__.__dict__[m]]
+    if overriden_members:
+      raise ValueError(
+          'Subclasses of Estimator cannot override members of Estimator. '
+          '{} does override {}'.format(self.__class__, overriden_members))
+
   def _get_features_from_input_fn(self, input_fn):
     result = input_fn()
     if not ops.get_default_graph().get_collection(ops.GraphKeys.QUEUE_RUNNERS):
diff --git a/tensorflow/python/estimator/estimator_test.py b/tensorflow/python/estimator/estimator_test.py
index 1aadba0743..9748be6da5 100644
--- a/tensorflow/python/estimator/estimator_test.py
+++ b/tensorflow/python/estimator/estimator_test.py
@@ -33,6 +33,38 @@ from tensorflow.python.training import session_run_hook
 from tensorflow.python.training import training
 
 
+def dummy_model_fn(features, labels, params):
+  _, _, _ = features, labels, params
+
+
+class EstimatorInheritanceConstraintTest(test.TestCase):
+  """Tests that sub classes cannot override methods of Estimator."""
+
+  def test_override_a_method(self):
+    class _Estimator(estimator.Estimator):
+
+      def __init__(self):
+        super(_Estimator, self).__init__(model_fn=dummy_model_fn)
+
+      def predict(self, input_fn, predict_keys=None, hooks=None):
+        pass
+
+    with self.assertRaisesRegexp(
+        ValueError, 'cannot override members of Estimator.*predict'):
+      _Estimator()
+
+  def test_extension_of_api_is_ok(self):
+    class _Estimator(estimator.Estimator):
+
+      def __init__(self):
+        super(_Estimator, self).__init__(model_fn=dummy_model_fn)
+
+      def predict_proba(self, input_fn, predict_keys=None, hooks=None):
+        pass
+
+    _Estimator()
+
+
 class EstimatorConstructorTest(test.TestCase):
 
   def test_config_must_be_a_run_config(self):
-- 
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