code: public static <T1> Func1<T1, Void> toFunc(final Action1<T1> action) {
          return toFunc(action, (Void) null);
      }
docs: Converts an {@link Action1} to a function that calls the action and returns {@code null}.
  
  @param action the {@link Action1} to convert
  @return a {@link Func1} that calls {@code action} and returns {@code null}