class Rouge::InheritableHash

def [](k)
  _sup = super
  return _sup if own_keys.include?(k)
  _sup || parent[k]
end

def each(&b)
  keys.each do |k|
    b.call(k, self[k])
  end
end

def include?(k)
  super or parent.include?(k)
end

def initialize(parent=nil)
  @parent = parent
end

def keys
  keys = own_keys.concat(parent.keys)
  keys.uniq!
  keys
end

def parent
  @parent ||= {}
end