OpenNMT-tf 2.10.0

New features

• Update to TensorFlow 2.2 and TensorFlow Addons 0.10
• Inputters can override the method keep_for_training to customize data filtering during the training

Fixes and improvements

• Fix serving function for language models
• Fix possible crash when using the prf evaluator
• Reduce time to start the training by optimizing the computation of the training data size
• Add more logs during inference to indicate that progress is being made and the process is not "stuck"
• Update SacreBLEU to 1.4.9