code: public ResourceBundle getResourceBundle() {
          for (Category c = this; c != null; c = c.parent) {
              if (c.resourceBundle != null)
                  return c.resourceBundle;
          }
          // It might be the case that there is no resource bundle
          return null;
      }
docs: Return the <em>inherited</em> {@link ResourceBundle} for this category.
  
  <p>
  This method walks the hierarchy to find the appropriate resource bundle. It will return the resource bundle attached to the closest
  ancestor of this category, much like the way priorities are searched. In case there is no bundle in the hierarchy then
  <code>null</code> is returned.
  
  @since 0.9.0