def get( index )
      raise "Only positive indexes, #{index}" if index < 0
      if index >= data_length
        return nil unless next_list
        return next_list.get( index - data_length)
      else
        ret = nil
        if(index < get_length)
          ret = get_internal_word(index + self.class.type_length )
        end
        return ret
      end
    end
def get( index )
      raise "Only positive indexes, #{index}" if index < 0
      if index >= data_length
        return nil unless next_list
        return next_list.get( index - data_length)
      else
        ret = nil
        if(index < get_length)
          ret = get_internal_word(index + self.class.type_length )
        end
        return ret
      end
    end
set the value at index.
 Lists start from index 0