XML declaration with xmlbf

Question

It is necessary to develop an api that would use the xml format for responses.

<?xml version="1.0" encoding="UTF-8" ?>
<response>
  <result>0</result>  
</response>

I am using the servant and servant-xml libraries.

newtype Response = Response
  { result :: Int }

instance ToXml Response where
  toXml r = element "response" HM.empty 
    $ element "result" HM.empty (text $ T.pack . show $ result r)

type API = Get '[XML] Response

proxy :: Proxy API
proxy = Proxy

server :: Server API
server = pure $ Response 0

main :: IO ()
main = run 8080 $ serve proxy server

and get

<response>
  <result>0</result>
</response>

xmlbf library (which servant-xml uses) has the ability to work with nodes and elements (element and text functions from the example above). Is it possible to add xml declaration using xmlbf?