al/bert preprocessing is broken after introducing electra support

Hello,

in this commit https://github.com/aws-samples/deep-learning-models/commit/bda976272e0db701032048f99a378bb897603dc8#diff-5a2807208d1060158af5c82c1f4aeeabae671e48574a00c70c830b66855c11b6L93
the function that was used to generate the examples for mlm and next sentence predictions are now removed. is this intentional? 