code: public function add($key, $value)
  	{
  		try
  		{
  			$this->getRecursive($key, $this->data);
  		}
  		catch (ElementNotFoundException $e)
  		{
  			$this->set($key, $value);
  		}
  	}
docs: Sets the value, if the does not exists yet
  
  @param $key string
  @param $value mixed
  @throws InvalidArgumentException
  @throws UnsupportedException
  @return void