code: func (s *ChangesService) DeleteReviewed(changeID, revisionID, fileID string) (*Response, error) {
  	u := fmt.Sprintf("changes/%s/revisions/%s/files/%s/reviewed", changeID, revisionID, url.PathEscape(fileID))
  	return s.client.DeleteRequest(u, nil)
  }
docs: // DeleteReviewed deletes the reviewed flag of the calling user from a file of a revision.
  //
  // Gerrit API docs: https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#delete-reviewed