public function create_evidence_item($evidence_item, $credential_id){

        $client = new \GuzzleHttp\Client();

        $response = $client->post($this->api_endpoint.'credentials/'.$credential_id.'/evidence_items', array(
            'headers' =>  array('Authorization' => 'Token token="'.$this->getAPIKey().'"'),
            'json' => $evidence_item
        ));

        $result = json_decode($response->getBody());

        return $result;
    }