def []=(name, value)
    name_pair = name_to_a(name).freeze
    hooks = assign(name_pair, value)
    hooks.each do |hook|
      hook.call(name_pair, value)
    end
    value
  end
def []=(name, value)
    name_pair = name_to_a(name).freeze
    hooks = assign(name_pair, value)
    hooks.each do |hook|
      hook.call(name_pair, value)
    end
    value
  end
name: a Symbol, String or an Array
 value: an Object