docs: def get_system_application_data_directory():
      """
      Returns the system Application data directory.
  
      Examples directories::
  
          - 'C:\\Users\\$USER\\AppData\\Roaming' on Windows 7.
          - 'C:\\Documents and Settings\\$USER\\Application Data' on Windows XP.
          - '/Users/$USER/Library/Preferences' on Mac Os X.
          - '/home/$USER' on Linux.
  
      :return: User Application data directory.
      :rtype: unicode
      """
  
      if platform.system() == "Windows" or platform.system() == "Microsoft":
          environment = Environment("APPDATA")
          return environment.get_value()
      elif platform.system() == "Darwin":
          environment = Environment("HOME")
          return os.path.join(environment.get_value(), "Library", "Preferences")
      elif platform.system() == "Linux":
          environment = Environment("HOME")
          return environment.get_value()