match_mediatype ::=
    "with-any-mediatype"
  | "(" "with-mediatype-equal-to" <mediatype> ")"
  | "(" "with-mediatype-not-equal-to" <mediatype> ")"
  | "(" "with-mediatype-similar-to" <string> ")"
  | "(" "with-mediatype-not-similar-to" <string> ")"
  ;
