gistfile1.php

/**
 * Implements hook_theme().
 */
function product_attribute_theme() {
  return array(
    'product_attribute_formatter_product_attribute' => array(
      'arguments' => array('element' => NULL),
    ),
  );
}

/**
 * Implements hook_field_formatter_info().
 */
function product_attribute_field_formatter_info() {
  return array(
    'product_attribute' => array(
      'label' => 'Product Attribute',
      'description' => t('an Attribute of a Product'),
      'field types' => array('content_taxonomy', 'text'),
      'multiple values' => CONTENT_HANDLE_MODULE,
    ),
  );
}

function theme_product_attribute_formatter_product_attribute($element) {
  return ($element['#item']['value'])
}