docs: def _add_user_to_file(file_id, service, user_email,
                        perm_type='user', role='writer'):
      """
      Grants the given set of permissions for a given file_id. service is an
      already-credentialed Google Drive service instance.
      """
      new_permission = {
          'value': user_email,
          'type': perm_type,
          'role': role
      }
      try:
          service.permissions()\
              .insert(fileId=file_id, body=new_permission)\
              .execute()
      except errors.HttpError as error:
          show_error('An error adding users to spreadsheet: {0}'.format(error))