code: public function editSource($row, $href, $label, $title, $icon, $attributes)
  	{
  		if (!$this->User->hasAccess('f5', 'fop'))
  		{
  			return '';
  		}
  
  		$strDecoded = rawurldecode($row['id']);
  		$rootDir = Contao\System::getContainer()->getParameter('kernel.project_dir');
  
  		if (is_dir($rootDir . '/' . $strDecoded))
  		{
  			return '';
  		}
  
  		$objFile = new Contao\File($strDecoded);
  
  		if (!\in_array($objFile->extension, Contao\StringUtil::trimsplit(',', strtolower(Contao\Config::get('editableFiles')))))
  		{
  			return Contao\Image::getHtml(preg_replace('/\.svg$/i', '_.svg', $icon)).' ';
  		}
  
  		return '<a href="'.$this->addToUrl($href.'&amp;id='.$row['id']).'" title="'.Contao\StringUtil::specialchars($title).'"'.$attributes.'>'.Contao\Image::getHtml($icon, $label).'</a> ';
  	}
docs: Return the edit file source button
  
  @param array  $row
  @param string $href
  @param string $label
  @param string $title
  @param string $icon
  @param string $attributes
  
  @return string