private static Implementation getRestrictionCoderDelegation( TypeDescription doFnType, DoFnSignature signature) { if (signature.processElement().isSplittable()) { if (signature.getRestrictionCoder() == null) { return MethodDelegation.to( new DefaultRestrictionCoder(signature.getInitialRestriction().restrictionT())); } else { return new DowncastingParametersMethodDelegation( doFnType, signature.getRestrictionCoder().targetMethod()); } } else { return ExceptionMethod.throwing(UnsupportedOperationException.class); } }