code: public static ProductCustomAttribute createCustomAttribute(
        ProductDimensionType productDimensionType, @Nullable String attributeValue) {
      Preconditions.checkNotNull(productDimensionType,
          "ProductDimensionType is required when creating a ProductCustomAttribute");
      ProductCustomAttribute productCustomAttribute = new ProductCustomAttribute();
      productCustomAttribute.setType(productDimensionType);
      productCustomAttribute.setValue(attributeValue);
      return productCustomAttribute;
    }
docs: Creates a new ProductCustomAttribute.
  
  @param productDimensionType required
  @param attributeValue may be null if creating an "other" dimension