def []=(key, value)
      if config = configs[key]
        config.set(receiver, value)
      else
        store[key] = value
      end
    end
def []=(key, value)
      if config = configs[key]
        config.set(receiver, value)
      else
        store[key] = value
      end
    end
Stores a value for the key, either on the receiver or in the store.