# File lib/multi_xml/parsers/ox.rb, line 79
        def append(key, value)
          key = key.to_s
          h = @stack.last
          if h.has_key?(key)
            v = h[key]
            if v.is_a?(Array)
              v << value
            else
              h[key] = [v, value]
            end
          else
            h[key] = value
          end
        end