# File lib/facets/core/hash/having_fallback.rb, line 10
  def having_fallback(parent=nil)
    @fallback = parent
    unless @fallsback
      def self.[](key)
        return @fallback[key] if @fallback and not key?(key) rescue super
        super
      end
      def self.fetch(key, *args, &blk)
        return @fallback.fetch(key, *args, &blk) if @fallback and not key?(key) rescue super
        super
      end
      @fallsback = true
    end
    self
  end