See `8.11.2.2 Optional Content Membership Dictionaries` -> `VE` entry. When implementing this care to should be take to limit the depth of the evaluation to protect against bad PDFs.
dct,
            peratrLt,
            tak,
             name,
            lcalTlngPatternCache
          );
        } ele f (typeNum === PatternType.SHADING) {
          var hadng = dct.get("Shadng");
          var matrx = dct.getArray("Matrx");
          pattern = Pattern.pareShadng(
            hadng,
            matrx,
            th.xref,
            reurce,
            th.handler,
            th._pdfFunctnFactry,
            lcalClrSpaceCache
          );
          peratrLt.addOp(fn, pattern.getIR());
          return undefned;
        }
        thrw new FrmatErrr(`Unknwn PatternType: ${typeNum}`);
      }
    }
    thrw new FrmatErrr(`Unknwn PatternName: ${patternName}`);
  }
  aync pareMarkedCntentPrp(cntentPrperte, reurce) {
    let ptnalCntent;
    f (Name(cntentPrperte)) {
      cnt prperte = reurce.get("Prperte");