original_string: public static function revert_submissions_to_draft($assignmentid, $userids) {
          global $CFG;
  
          $params = self::validate_parameters(self::revert_submissions_to_draft_parameters(),
                          array('assignmentid' => $assignmentid,
                                'userids' => $userids));
  
          list($assignment, $course, $cm, $context) = self::validate_assign($params['assignmentid']);
  
          $warnings = array();
          foreach ($params['userids'] as $userid) {
              if (!$assignment->revert_to_draft($userid)) {
                  $detail = 'User id: ' . $userid . ', Assignment id: ' . $params['assignmentid'];
                  $warnings[] = self::generate_warning($params['assignmentid'],
                                                       'couldnotrevert',
                                                       $detail);
              }
          }
  
          return $warnings;
      }
code: public static function revert_submissions_to_draft($assignmentid, $userids) {
          global $CFG;
  
          $params = self::validate_parameters(self::revert_submissions_to_draft_parameters(),
                          array('assignmentid' => $assignmentid,
                                'userids' => $userids));
  
          list($assignment, $course, $cm, $context) = self::validate_assign($params['assignmentid']);
  
          $warnings = array();
          foreach ($params['userids'] as $userid) {
              if (!$assignment->revert_to_draft($userid)) {
                  $detail = 'User id: ' . $userid . ', Assignment id: ' . $params['assignmentid'];
                  $warnings[] = self::generate_warning($params['assignmentid'],
                                                       'couldnotrevert',
                                                       $detail);
              }
          }
  
          return $warnings;
      }
code_tokens: public static function revert_submissions_to_draft ( $ assignmentid , $ userids ) { global $ CFG ; $ params = self :: validate_parameters ( self :: revert_submissions_to_draft_parameters ( ) , array ( 'assignmentid' => $ assignmentid , 'userids' => $ userids ) ) ; list ( $ assignment , $ course , $ cm , $ context ) = self :: validate_assign ( $ params [ 'assignmentid' ] ) ; $ warnings = array ( ) ; foreach ( $ params [ 'userids' ] as $ userid ) { if ( ! $ assignment -> revert_to_draft ( $ userid ) ) { $ detail = 'User id: ' . $ userid . ', Assignment id: ' . $ params [ 'assignmentid' ] ; $ warnings [ ] = self :: generate_warning ( $ params [ 'assignmentid' ] , 'couldnotrevert' , $ detail ) ; } } return $ warnings ; }
docstring: Reverts a list of user submissions to draft for a single assignment.
  
  @param int $assignmentid The id of the assignment
  @param array $userids Array of user ids to revert
  @return array of warnings for each submission that could not be reverted.
  @since Moodle 2.6
docstring_tokens: Reverts a list of user submissions to draft for a single assignment .