code: public static <T, R, E extends Throwable> @NonNull Function<T, R> rethrowFunction(final @NonNull ThrowingFunction<T, R, E> function) {
      return function;
    }
docs: Returns the same throwing function.
  
  @param function the function
  @param <T> the input type
  @param <R> the output type
  @param <E> the exception type
  @return the function