code: private static XsdList getAttributeList(XsdAttribute attribute) {
          return attribute.getXsdSimpleType() != null ? attribute.getXsdSimpleType().getList() : null;
      }
docs: Returns the {@link XsdList} of the {@link XsdAttribute} object.
  @param attribute The {@link XsdAttribute} object.
  @return The contained {@link XsdList} object or null if not present.