code: public final FunctionType forgetParameterAndReturnTypes() {
      FunctionType result =
          builder(registry)
              .withName(getReferenceName())
              .withSourceNode(source)
              .withTypeOfThis(getInstanceType())
              .withKind(kind)
              .build();
      result.setPrototypeBasedOn(getInstanceType());
      return result;
    }
docs: Create a new constructor with the parameters and return type stripped.