OpenNMT-tf 2.21.0

New features

• Support TensorFlow 2.6
• Add tokenizer SentencePieceTokenizer, an in-graph SentencePiece tokenizer provided by tensorflow-text
• Add methods to facilitate training a Model instance:
  • model.compute_training_loss
  • model.compute_gradients
  • model.train
• Add --output_file argument to score command

Fixes and improvements

• Fix make_features method of inputters WordEmbedder and SequenceRecordInputter to work on a batch of elements
• Fix error when SelfAttentionDecoder is called without memory_sequence_length
• Fix ConvEncoder on variable-length inputs
• Support SacreBLEU 2.0