```ruby
require 'device_api/sys_log'

module DeviceAPI
  attr_accessor :log

  @@log = DeviceAPI::SysLog.new

  def self.set_logger(log)
    @@log = log
  end

  def self.log
    @@log
  end
end```

Define device missing and unauthorized exceptions
user
```ruby
require 'device_api/sys_log'

module DeviceAPI
  attr_accessor :log

  class UnauthorizedDevice < StandardError; end
  class DeviceNotFound < StandardError; end

  @@log = DeviceAPI::SysLog.new

  def self.set_logger(log)
    @@log = log
  end

  def self.log
    @@log
  end
end
```
assistant