code: @Override
    public Transformer<T> compose(Transformer<T> one, Transformer<T> two) {
      return one == null ? two : (two == null ? one : new ComposableTransformer<>(one, two));
    }
docs: Composes the given {@link Transformer Transformers} into a composite {@link Transformer}.
  
  @param one {@link Transformer} to compose.
  @param two {@link Transformer} to compose.
  @return a composite {@link Transformer} composed of the given {@link Transformer Transformers}.
  Returns {@code one} if {@code two} is {@literal null}; returns {@code two} if {@code one} is {@literal null}.
  @see #ComposableTransformer(Transformer, Transformer)