code: public Type[] getArrayIndexTypes() throws IntrospectionException {
          if (!mCheckedForArrayLookup) {
              checkForArrayLookup();
          }
  
          return mArrayIndexTypes == null ? null :
              (Type[])mArrayIndexTypes.clone();
      }
docs: If this Type supports array lookup, then return the index type. Because
  the index type may be overloaded, an array is returned.
  Null is returned if this Type doesn't support array lookup.