guidance to handle missing modality at test time

[AnilRahate]

Hi Paul,

I have read about Co-learning where we can train model on 3 modalities however at test time we can use only one modality. I am struggling to understand how this will be implemented in a code. Once we train a model with 3 modalities, it will expect 3 modalities at test time. Do we need to handle this scenario by passing zero or some random values for modalities to be dropped. Please help, also any sample implementation of the same.
Thanks a lot for all your awesome repo.