Fix fairseq/data/token_block_utils_fast.pyx
Fix fairseq/data/token_block_utils_fast.pyx

Summary: Pull Request resolved: https://github.com/fairinternal/fairseq-py/pull/951

Differential Revision: D19124622

Pulled By: myleott

fbshipit-source-id: a44b2fdc0834126829919bc8ad454ff1fbaa8627

pytorch/fairseq,pytorch/fairseq,pytorch/fairseq