code: public function getStyleSheets(Contao\DataContainer $dc)
  	{
  		$intPid = $dc->activeRecord->pid;
  
  		if (Contao\Input::get('act') == 'overrideAll')
  		{
  			$intPid = Contao\Input::get('id');
  		}
  
  		$objStyleSheet = $this->Database->prepare("SELECT id, name FROM tl_style_sheet WHERE pid=?")
  										->execute($intPid);
  
  		if ($objStyleSheet->numRows < 1)
  		{
  			return array();
  		}
  
  		$return = array();
  
  		while ($objStyleSheet->next())
  		{
  			$return[$objStyleSheet->id] = $objStyleSheet->name;
  		}
  
  		return $return;
  	}
docs: Return all style sheets of the current theme
  
  @param Contao\DataContainer $dc
  
  @return array