Simplify Subtype.list_to_string
Simplify Subtype.list_to_string

Reviewed By: jeremydubreil

Differential Revision: D4371339

fbshipit-source-id: 6c192f4

ryoon/infer,blzq/infer,xennygrimmato/infer,ryoon/infer,ropas/infer,jsachs/infer,ropas/infer,jsachs/infer,ryoon/infer,ropas/infer,ropas/infer,blzq/infer,blzq/infer,facebook/infer,ryoon/infer,kageiit/infer,blzq/infer,kageiit/infer,blzq/infer,kageiit/infer,facebook/infer,kageiit/infer,ryoon/infer,xennygrimmato/infer,kageiit/infer,jvillard/infer,xennygrimmato/infer,jvillard/infer,jvillard/infer,xennygrimmato/infer,xennygrimmato/infer,xennygrimmato/infer,ryoon/infer,xennygrimmato/infer,jvillard/infer,facebook/infer,ropas/infer,facebook/infer,kageiit/infer,jvillard/infer,jvillard/infer,ropas/infer,jvillard/infer,jsachs/infer,jsachs/infer,kageiit/infer,facebook/infer,facebook/infer,jsachs/infer,blzq/infer,jsachs/infer,facebook/infer