Fix KerasMetricCallback prediction with generate() and inference of column names (#15351)
* Fix prediction with generate() and the inference of column names
Should now have very few differences with the PyTorch implementation
* Minor edit to parent class
* Update src/transformers/keras_callbacks.py
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>
* Explaining the dict conversion
* Putting main_input_name back
* Fixes to main_input_name
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>