public function addSchemaToWsdl(Wsdl $wsdl, $schemaLocation)
    {
        if (!empty($schemaLocation) && $wsdl->getContent() instanceof WsdlDocument && $wsdl->getContent()->getExternalSchema($schemaLocation) === null) {
            $wsdl->getContent()->addExternalSchema(new Schema($wsdl->getGenerator(), $schemaLocation, $this->getUrlContent($schemaLocation)));
        }
        return $this;
    }