def unbind
      if bound?
        configs.each_pair do |key, config|
          store[key] = config.get(receiver)
        end
        @receiver = nil
      end
      self
    end
def unbind
      if bound?
        configs.each_pair do |key, config|
          store[key] = config.get(receiver)
        end
        @receiver = nil
      end
      self
    end
Unbinds the configs set on receiver by getting each value (via
 config.get) and setting the result into store. Does nothing if no
 receiver is set.