Adding API usage logging (#1318)
Adding API usage logging (#1318)

Summary: Adding API usage logging for Vocab module

Reviewed By: colin2328

Differential Revision: D28585537

fbshipit-source-id: 38975b523fb597412fbcb18ef831bfb4834cb420

Co-authored-by: Parmeet Singh Bhatia <7290e7de5dd623c3832a917e9fd987cb35500897@fb.com>
pytorch/text,pytorch/text,pytorch/text,pytorch/text