How to use org.apache.beam.sdk.transforms.reflect

@Setup
public void setup() {
 invoker = DoFnInvokers.invokerFor(splittableFn);
 invoker.invokeSetup();
}

 private static boolean isSplittable(DoFn<?, ?> fn) {
  return DoFnSignatures.signatureForDoFn(fn).processElement().isSplittable();
 }
}

public void checkArgument(boolean condition, String message, Object... args) {
 if (!condition) {
  throwIllegalArgument(message, args);
 }
}

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);
 }
}

private DoFn.ProcessContinuation invokeProcessElement(DoFn<String, String> fn) {
 return DoFnInvokers.invokerFor(fn).invokeProcessElement(mockArgumentProvider);
}

 static DoFnSignature.ProcessElementMethod analyzeProcessElementMethod(AnonymousMethod method)
   throws Exception {
  return DoFnSignatures.analyzeProcessElementMethod(
    errors(),
    TypeDescriptor.of(FakeDoFn.class),
    method.getMethod(),
    TypeDescriptor.of(Integer.class),
    TypeDescriptor.of(String.class),
    FnAnalysisContext.create());
 }
}

private static Implementation splitRestrictionDelegation(
  TypeDescription doFnType, DoFnSignature signature) {
 if (signature.splitRestriction() == null) {
  return MethodDelegation.to(DefaultSplitRestriction.class);
 } else {
  return new DowncastingParametersMethodDelegation(
    doFnType, signature.splitRestriction().targetMethod());
 }
}

private void invokeOnTimer(DoFn<String, String> fn, String timerId) {
 OnTimerInvokers.forTimer(fn, timerId).invokeOnTimer(mockArgumentProvider);
}

public void addTimerDeclarations(Iterable<TimerDeclaration> decls) {
 for (TimerDeclaration decl : decls) {
  addTimerDeclaration(decl);
 }
}

@Override
public void open(Configuration parameters) throws Exception {
 doFnInvoker = DoFnInvokers.invokerFor(doFn);
 doFnInvoker.invokeSetup();
}

 public void checkNotNull(Object value, String message, Object... args) {
  if (value == null) {
   throwIllegalArgument(message, args);
  }
 }
}

@Setup
public void setup() {
 DoFnInvokers.invokerFor(underlyingDoFn).invokeSetup();
}

@Setup
public void setup() throws Exception {
 invoker = DoFnInvokers.invokerFor(fn);
 invoker.invokeSetup();
}

@Override
public void open(Configuration parameters) throws Exception {
 doFnInvoker = DoFnInvokers.invokerFor(dofn);
 doFnInvoker.invokeSetup();
}

@Override
public void open(Configuration parameters) throws Exception {
 doFnInvoker = DoFnInvokers.invokerFor(dofn);
 doFnInvoker.invokeSetup();
}

@Setup
public void setup() {
 invoker = DoFnInvokers.invokerFor(fn);
 invoker.invokeSetup();
}

@Override
public void open(Configuration parameters) throws Exception {
 doFnInvoker = DoFnInvokers.invokerFor(doFn);
 doFnInvoker.invokeSetup();
}

@Setup
public void setup() {
 this.invoker = DoFnInvokers.invokerFor(fn);
 invoker.invokeSetup();
}

@Override
public void open(Configuration parameters) throws Exception {
 doFnInvoker = DoFnInvokers.invokerFor(dofn);
 doFnInvoker.invokeSetup();
}

@Override
public void open(Configuration parameters) throws Exception {
 doFnInvoker = DoFnInvokers.invokerFor(doFn);
 doFnInvoker.invokeSetup();
}