code: public static <T1, T2> Func2<T1, T2, Void> toFunc(final Action2<T1, T2> action) {
          return toFunc(action, (Void) null);
      }
docs: Converts an {@link Action2} to a function that calls the action and returns {@code null}.
  
  @param action the {@link Action2} to convert
  @return a {@link Func2} that calls {@code action} and returns {@code null}