code: public function checkStyleSheetName($strName)
  	{
  		$objStyleSheet = $this->Database->prepare("SELECT COUNT(*) AS count FROM tl_style_sheet WHERE name=?")
  										->limit(1)
  										->execute($strName);
  
  		if ($objStyleSheet->count < 1)
  		{
  			return $strName;
  		}
  
  		$chunks = explode('-', $strName);
  		$i = (\count($chunks) > 1) ? array_pop($chunks) : 0;
  		$strName = implode('-', $chunks) . '-' . ((int) $i + 1);
  
  		return $this->checkStyleSheetName($strName);
  	}
docs: Check the name of an imported file
  
  @param string $strName
  
  @return string