Classes/ViewHelpers/ViewColumnViewHelper.php
public function render(int $viewColumn, $data) {
    $output       = '';
    $viewChildren = $data['tx_gridelements_view_children'];
    $viewChildren = $this->filterViewChildrenByViewColumn($viewChildren, $viewColumn);

    if ($this->extensionService->runningInStrictMode()) {
      $viewChildren = $this->filterViewChildrenBySysLanguage($viewChildren);
    }

    foreach($viewChildren as $viewChild) {
      $uid              = $viewChild['uid'];
      $viewChildId      = "tx_gridelements_view_child_{$uid}";
      $viewChildContent = $data[$viewChildId];

      if (!empty($viewChildContent)) {
        $output .= $viewChildContent;
      }
    }

    return $output;
  }
public function render(int $viewColumn, $data) {
    $output       = '';
    $viewChildren = $data['tx_gridelements_view_children'];
    $viewChildren = $this->filterViewChildrenByViewColumn($viewChildren, $viewColumn);

    if ($this->extensionService->runningInStrictMode()) {
      $viewChildren = $this->filterViewChildrenBySysLanguage($viewChildren);
    }

    foreach($viewChildren as $viewChild) {
      $uid              = $viewChild['uid'];
      $viewChildId      = "tx_gridelements_view_child_{$uid}";
      $viewChildContent = $data[$viewChildId];

      if (!empty($viewChildContent)) {
        $output .= $viewChildContent;
      }
    }

    return $output;
  }
The view helper render function.

@param int $viewColumn The UID of the view column
@param array $data The page data
@return string The rendered content of the view column