Merged commit includes the following changes:

187187978  by Zhichao Lu:

    Only updating hyperparameters if they have non-null values.

--
187097690  by Zhichao Lu:

    Rewrite some conditions a bit more clearly.

--
187085190  by Zhichao Lu:

    More informative error message.

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186935376  by Zhichao Lu:

    Added option to evaluator.evaluate to use custom evaluator objects.

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186808249  by Zhichao Lu:

    Fix documentation re: number of stages.

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186775014  by Zhichao Lu:

    Change anchor generator interface to return a list of BoxLists containing anchors for different feature map layers.

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186729028  by Zhichao Lu:

    Minor fixes to object detection.

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186723716  by Zhichao Lu:

    Fix tf_example_decoder.py initailization issue.

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186668505  by Zhichao Lu:

    Remove unused import.

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186475361  by Zhichao Lu:

    Update the box predictor interface to return list of predictions - one from each feature map - instead of stacking them into one large tensor.

--
186410844  by Zhich...

research/object_detection/utils/json_utils.py

+# 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.
+# ==============================================================================
 """Utilities for dealing with writing json strings.
 
 json_utils wraps json.dump and json.dumps so that they can be used to safely

research/object_detection/utils/json_utils_test.py

+# 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.
+# ==============================================================================
 """Tests for google3.image.understanding.object_detection.utils.json_utils."""
 import os
 

research/object_detection/utils/learning_schedules.py

@@ -142,6 +142,7 @@ def manual_stepping(global_step, boundaries, rates):
   if len(rates) != len(boundaries) + 1:
     raise ValueError('Number of provided learning rates must exceed '
                      'number of boundary points by exactly 1.')
+  if not boundaries: return tf.constant(rates[0])
   step_boundaries = tf.constant(boundaries, tf.int32)
   num_boundaries = len(boundaries)
   learning_rates = tf.constant(rates, tf.float32)

research/object_detection/utils/learning_schedules_test.py

@@ -75,5 +75,21 @@ class LearningSchedulesTest(test_case.TestCase):
     exp_rates = [1.0, 1.0, 2.0, 3.0, 3.0, 3.0, 3.0, 4.0, 4.0, 4.0]
     self.assertAllClose(output_rates, exp_rates)
 
+  def testManualSteppingWithZeroBoundaries(self):
+    def graph_fn(global_step):
+      boundaries = []
+      rates = [0.01]
+      learning_rate = learning_schedules.manual_stepping(
+          global_step, boundaries, rates)
+      return (learning_rate,)
+
+    output_rates = [
+        self.execute(graph_fn, [np.array(i).astype(np.int64)])
+        for i in range(4)
+    ]
+    exp_rates = [0.01] * 4
+    self.assertAllClose(output_rates, exp_rates)
+
+
 if __name__ == '__main__':
   tf.test.main()

research/object_detection/utils/np_box_list_ops.py

@@ -19,7 +19,6 @@ Example box operations that are supported:
   * Areas: compute bounding box areas
   * IOU: pairwise intersection-over-union scores
 """
-
 import numpy as np
 
 from object_detection.utils import np_box_list

research/object_detection/utils/np_box_mask_list_ops.py

@@ -19,7 +19,6 @@ Example box operations that are supported:
   * Areas: compute bounding box areas
   * IOU: pairwise intersection-over-union scores
 """
-
 import numpy as np
 
 from object_detection.utils import np_box_list_ops

research/object_detection/utils/ops.py

@@ -224,7 +224,7 @@ def padded_one_hot_encoding(indices, depth, left_pad):
     ValueError: if `indices` does not have rank 1 or if `left_pad` or `depth are
       either negative or non-integers.
 
-  TODO: add runtime checks for depth and indices.
+  TODO(rathodv): add runtime checks for depth and indices.
   """
   if depth < 0 or not isinstance(depth, six.integer_types):
     raise ValueError('`depth` must be a non-negative integer.')
@@ -474,7 +474,7 @@ def normalize_to_target(inputs,
   Note that the rank of `inputs` must be known and the dimension to which
   normalization is to be applied should be statically defined.
 
-  TODO: Add option to scale by L2 norm of the entire input.
+  TODO(jonathanhuang): Add option to scale by L2 norm of the entire input.
 
   Args:
     inputs: A `Tensor` of arbitrary size.
@@ -704,7 +704,7 @@ def reframe_box_masks_to_image_masks(box_masks, boxes, image_height,
   Returns:
     A tf.float32 tensor of size [num_masks, image_height, image_width].
   """
-  # TODO: Make this a public function.
+  # TODO(rathodv): Make this a public function.
   def transform_boxes_relative_to_boxes(boxes, reference_boxes):
     boxes = tf.reshape(boxes, [-1, 2, 2])
     min_corner = tf.expand_dims(reference_boxes[:, 0:2], 1)

research/object_detection/utils/shape_utils.py

@@ -152,7 +152,7 @@ def static_or_dynamic_map_fn(fn, elems, dtype=None,
   Tensors or lists of Tensors).  Likewise, the output of `fn` can only be a
   Tensor or list of Tensors.
 
-  TODO: make this function fully interchangeable with tf.map_fn.
+  TODO(jonathanhuang): make this function fully interchangeable with tf.map_fn.
 
   Args:
     fn: The callable to be performed. It accepts one argument, which will have

research/object_detection/utils/test_case.py

+# 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.
+# ==============================================================================
 """A convenience wrapper around tf.test.TestCase to enable TPU tests."""
 
 import tensorflow as tf

research/object_detection/utils/variables_helper.py

@@ -23,7 +23,7 @@ import tensorflow as tf
 slim = tf.contrib.slim
 
 
-# TODO: Consider replacing with tf.contrib.filter_variables in
+# TODO(derekjchow): Consider replacing with tf.contrib.filter_variables in
 # tensorflow/contrib/framework/python/ops/variables.py
 def filter_variables(variables, filter_regex_list, invert=False):
   """Filters out the variables matching the filter_regex.
@@ -104,7 +104,7 @@ def get_variables_available_in_checkpoint(variables,
   Inspects given checkpoint and returns the subset of variables that are
   available in it.
 
-  TODO: force input and output to be a dictionary.
+  TODO(rathodv): force input and output to be a dictionary.
 
   Args:
     variables: a list or dictionary of variables to find in checkpoint.

research/object_detection/utils/visualization_utils_test.py

@@ -13,12 +13,7 @@
 # limitations under the License.
 # ==============================================================================
 
-"""Tests for image.understanding.object_detection.core.visualization_utils.
-
-Testing with visualization in the following colab:
-https://drive.google.com/a/google.com/file/d/0B5HnKS_hMsNARERpU3MtU3I5RFE/view?usp=sharing
-
-"""
+"""Tests for image.understanding.object_detection.core.visualization_utils."""
 import logging
 import os