if( tags_.find( key ) != tags_.end() )
std::map< QString, cVariant >::iterator iter = tags_.find( key );  if( iter != tags_.end() )
	void		set( QString key, cVariant value ) 	{		if( tags_.find( key ) != tags_.end() )		{			if( !value.isValid() )				this->tags_.erase( tags_.find( key ) );			else				tags_.find( key )->second = value;		}		else			this->tags_.insert(std::make_pair(key, value)); 	}