Update TensorFlow version to 2.2
Hi there!!I’m gathering some feebacks from the community in order to know what you guys think to fix the minimum TensorFlow version to 2.2?This would allow the models to be compliant with several cool features such as:Model.train_stepmethod to create simple custom training loop that can be used withModel.fitPre-computed SavedModel inputs/outputs withModel._saved_model_inputs_specMake use of the newtf.data.experimental.assert_cardinalitythat can fix a size to a TFRecord orfrom_generatorTensorFlow Datasets.Drop the Python 2 support such as transformers itself.Let me know here all your suggestions about this