added more descriptive comment to urgent change
added more descriptive comment to urgent change

Summary: Added description of problem and task associated with it in code

Reviewed By: dianaml0

Differential Revision: D29942196

fbshipit-source-id: 037d92af720f52bdd51f4efc5b9d49a6465cdd31

pytorch/fairseq,pytorch/fairseq,pytorch/fairseq