protected function payload(RequestInterface $request, StructureShape $member, array $value)
 {
     $request->setHeader('Content-Type', 'application/xml');
     $request->setBody(Stream::factory($this->xmlBody->build($member, $value)));
 }
 protected function payload(StructureShape $member, array $value, array &$opts)
 {
     $opts['headers']['Content-Type'] = 'application/xml';
     $opts['body'] = (string) $this->xmlBody->build($member, $value);
 }