class TrackingNumber::Info

def initialize(info_hash = {})
  info_hash.keys.each do |key|
    self.instance_variable_set("@#{key}", info_hash[key])
    self.class_eval { attr_accessor key }
  end
  if info_hash.keys.size == 1
    @default = info_hash[info_hash.keys.first]
  end
end