public function dynamicMetrics($filter, $start, $end, $inventoryFilter=Null){
        $urlencoded = '';
        $query = array();
        if (isset($inventoryFilter)){
            $query['inventoryFilter'] = $inventoryFilter;
        }
        if (!empty($query)){
            $urlencoded = '?' . http_build_query($query);
        }

        $param = array(
            'start' => date("Y-m-d\TH:i:s\Z", $start),
            'end' => date("Y-m-d\TH:i:s\Z", $end),
            'filter' => $filter
        );

        $param = $this->makeJsonReady($param);

        return $this->get('metrics/dynamicgraphs/' . $urlencoded, $param);
    }