def short_out(io,level)
      io.write("{")
      @children.each_with_index do |child , i|
        key , val = child
        key.out(io , level + 1)
        io.write " => "
        val.out(io , level + 1)
        io.write ", " unless (i+1) == @children.length
      end
      io.write("}")
    end
def short_out(io,level)
      io.write("{")
      @children.each_with_index do |child , i|
        key , val = child
        key.out(io , level + 1)
        io.write " => "
        val.out(io , level + 1)
        io.write ", " unless (i+1) == @children.length
      end
      io.write("}")
    end
This defines the short output which is basically what you would write in ruby
 ie { key1 => value1 , ... }
 The short is used for 7 or less SimpleNodes