code: func (s *ProjectsService) DeleteBranches(projectName string, input *DeleteBranchesInput) (*Response, error) {
  	u := fmt.Sprintf("projects/%s/branches:delete", url.QueryEscape(projectName))
  	return s.client.DeleteRequest(u, input)
  }
docs: // DeleteBranches delete one or more branches.
  // If some branches could not be deleted, the response is “409 Conflict” and the error message is contained in the response body.
  //
  // Gerrit API docs: https://gerrit-review.googlesource.com/Documentation/rest-api-projects.html#delete-branches