Fix comments in FileImpl (#712)
Fix comments in FileImpl (#712)

* Fix comments in FileImpl

(#711)

* Fix indent & spell

(#711)

lylei/dfs,lylei/dfs,baidu/bfs,bluebore/dfs,yvxiang/dfs,bluebore/dfs,bluebore/bfs,linyvxiang/dfs,yvxiang/coverage_for_bfs,linyvxiang/dfs,linyvxiang/dfs,yvxiang/dfs,bluebore/bfs,lylei/dfs,baidu/bfs,yvxiang/coverage_for_bfs,bluebore/dfs,bluebore/bfs,yvxiang/dfs,baidu/bfs,yvxiang/dfs,yvxiang/coverage_for_bfs,yvxiang/coverage_for_bfs,lylei/dfs,baidu/bfs