FutureWarning Issued by create_pet_tf_record.py

[WillAyd]

When following through the instructions in models/research/object_detection/g3doc/running_pets.md the python script generates a FutureWarning from lxml:

/Users/williamayd/clones/models/research/object_detection/utils/dataset_util.py:75: FutureWarning: The behavior of this method will change in future versions. Use specific 'len(elem)' or 'elem is not None' test instead.
  if not xml:

The offending line is below and the FutureWarning should be easily resolved if replace with the more explicit len(xml):

https://github.com/tensorflow/models/blob/29c9f9855711006704b8fa9364f966d67694287e/research/object_detection/utils/dataset_util.py#L75

I would be happy to submit a PR to clean this up

System information

• What is the top-level directory of the model you are using: models/research

• Have I written custom code (as opposed to using a stock example script provided in TensorFlow): Stock example

• OS Platform and Distribution (e.g., Linux Ubuntu 16.04): macOS High Sierra 10.13.5

• TensorFlow installed from (source or binary): Source

• TensorFlow version (use command below): v1.8.0-0-g93bc2e2072 1.8.0

• Bazel version (if compiling from source): bazel release 0.14.1-homebrew

• CUDA/cuDNN version:

• GPU model and memory:

• Exact command to reproduce: Taken directly from models/research/object_detection/g3doc/running_pets.md:

  python object_detection/dataset_tools/create_pet_tf_record.py \
  --label_map_path=object_detection/data/pet_label_map.pbtxt \
  --data_dir=`pwd` \
  --output_dir=`pwd`

Describe the problem

The xml parsing code issues a warning from lxml for the boolean check it performs to detect whether or not there are child elements. If lxml changes this behavior in the future this code will break.

Source code / logs

Provided again for reference. Here is the offending line:

https://github.com/tensorflow/models/blob/29c9f9855711006704b8fa9364f966d67694287e/research/object_detection/utils/dataset_util.py#L75

And the warning that it generates:

/Users/williamayd/clones/models/research/object_detection/utils/dataset_util.py:75: FutureWarning: The behavior of this method will change in future versions. Use specific 'len(elem)' or 'elem is not None' test instead.
  if not xml:

[pkulzc]

@WillAyd Thanks for noticing this! If you would like to, please simply send a PR to fix this and I'll review and merge it.

[pkulzc]

Thanks for the fix!