code: public Throwable unwrap() {
  		Throwable cause = getCause();
  		return (cause instanceof WrappingRuntimeException) ? ((WrappingRuntimeException) cause).unwrap() : cause;
  	}
docs: Recursively unwraps this WrappingRuntimeException and its causes, getting the first
  non wrapping exception.
  
  @return The first cause that is not a wrapping exception.