code: function quotedString() {
          return wrap('quoted-string', and(
              invis(opt(cfws)),
              invis(dquote), star(and(opt(colwsp(fws)), qcontent)), opt(invis(fws)), invis(dquote),
              invis(opt(cfws))
          )());
      }
docs: quoted-string   =   [CFWS] DQUOTE *([FWS] qcontent) [FWS] DQUOTE [CFWS]