anchor.diff:  resource_exists(_) -> 'true'.
   resource_exists(?CARRIERS,_) -> 'true';
   resource_exists(?MODB,_) -> 'true'.
  -resource_exists(?CARRIERS,_,?ATTACHMENT) -> 'true';
  +resource_exists(?CARRIERS,_,_) -> 'true';
   resource_exists(?MODB,_,?ATTACHMENT) -> 'true'.
   
   -spec content_types_provided(cb_context:context()) -> cb_context:context().
  
positive.code:     Context.
  content_types_provided(Context,_,?GENERATE) ->
      Context.
  content_types_provided(Context,?MODB,_,?ATTACHMENT) ->
      CTP = [{'to_binary', [{<<"application">>, <<"pdf">>}]}],
      cb_context:set_content_types_provided(Context, CTP).
  
negative.code:     validate_onbill(Context, Id, cb_context:req_verb(Context)).
  validate(Context, ?CARRIERS, Id) ->
      validate_onbill(Context, ?CARRIERS, Id, cb_context:req_verb(Context)).
  validate(Context,?CARRIERS, Id, AttachmentId) ->
      validate_onbill(Context,?CARRIERS, Id, AttachmentId, cb_context:req_verb(Context));
  validate(Context,?MODB, Id, ?ATTACHMENT) ->
      validate_onbill(Context,?MODB, Id, ?ATTACHMENT, cb_context:req_verb(Context)).
  
  