public function _request($body)
    {
        if(isset($body['params'])){
            $response = $this->client->send($this->client->request(0, $body['method'], $body['params']));
        } else {
            $response = $this->client->send($this->client->request(0, $body['method']));
        }
        $response = json_decode($response->getBody());
        // if there is an error, return the error message otherwise respond with result
        if(property_exists($response, 'error')){
            return json_encode($response->error);
        } else {
            return json_encode($response->result);
        }
    }