code: public function updateAfterRestore($id, $table, $data)
  	{
  		if ($table != 'tl_style')
  		{
  			return;
  		}
  
  		// Update the timestamp of the style sheet
  		$this->Database->prepare("UPDATE tl_style_sheet SET tstamp=? WHERE id=?")
  					   ->execute(time(), $data['pid']);
  
  		// Update the CSS file
  		$this->import('Contao\StyleSheets', 'StyleSheets');
  		$this->StyleSheets->updateStyleSheet($data['pid']);
  	}
docs: Update a style sheet after a version has been restored
  
  @param integer $id
  @param string  $table
  @param array   $data