code: static XsdElement getBaseFromElement(XsdElement element) {
          XsdExtension extension = getXsdExtension(element);
  
          return extension != null ? extension.getBase(): null;
      }
docs: Obtains the base attribute value from the {@link XsdExtension} from the received {@link XsdElement}.
  @param element The received {@link XsdElement} object.
  @return The base value of the received {@link XsdElement}.