Fix a bug in Bitransformer: Add encoder_sequence_id and decoder_sequence_id if they are missing.  These tensors are necessary to indicate padding. This bug affected cases where there was no example packing.
Fix a bug in Bitransformer:
Add encoder_sequence_id and decoder_sequence_id if they are missing.  These
tensors are necessary to indicate padding.
This bug affected cases where there was no example packing.

PiperOrigin-RevId: 308843111

tensorflow/mesh,tensorflow/mesh