anchor.diff:  get(path, RD) -> wrq:path(RD);
   get(qs, RD) -> wrq:req_qs(RD);
   get(headers, RD) -> wrq:req_headers(RD);
  +get(user_agent, RD) -> proplists:get_value("user-agent", wrq:req_headers(RD));
   get(_Key, _RD) -> undefined.
   
   
  
positive.code: -export([
      m_find_value/3,
      m_to_list/2,
      m_value/2
  ]).
  
  -include_lib("zotonic.hrl").
  
negative.code: 
  
  %% @doc Fetch the field from the wrq interface.
  get(What, #context{} = Context) -> get(What, z_context:get_reqdata(Context));
  get(_What, undefined) -> undefined;
  get(method, RD) -> wrq:method(RD);
  get(version, RD) -> wrq:version(RD);
  get(peer, RD) -> wrq:peer(RD);
  