What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

/kind bug

What does this PR do / why do we need it:

  1. modify api comments for DatasetHelper and loss_scale in optimizer
  2. clean pclint warning

Which issue(s) this PR fixes:

Fixes # https://e.gitee.com/mind_spore/projects/67813/milestones/30692/issues?is%5Bissue_type_id%5D=132101&issue=I4BFLT

Special notes for your reviewers: