old_contents: 
  from rez.config import config
  
  
  class Application(object):
      """An interface for registering custom Rez application/subcommand"""
      def __init__(self):
          self.type_settings = config.plugins.application
          self.settings = self.type_settings.get(self.name())
  
      @classmethod
      def name(cls):
          """Return the name of the Application and rez-subcommand."""
          raise NotImplementedError
  
new_contents: 
  from rez.config import config
  
  
  class Application(object):
      """An interface for registering custom Rez subcommand
  
      To register plugin and expose subcommand, the plugin module..
  
      * MUST have a module-level docstring (used as the command help)
      * MUST have a module-level attribute `command_behavior`
      * MUST provide a `setup_parser()` function
      * MUST provide a `command()` function
      * MUST provide a `register_plugin()` function
  
      For example, a plugin named 'foo' and this is the `foo.py`:
  
          '''The docstring for command help, this is required.
          '''
          from rez.application import Application
  
          command_behavior = {
              "hidden": False,   # optional: bool
              "arg_mode": None,  # optional: None, "passthrough", "grouped"
          }
  
          def setup_parser(parser, completions=False):
              parser.add_argument("--hello", ...)
  
          def command(opts, parser=None, extra_arg_groups=None):
              if opts.hello:
                  print("world")
  
          class ApplicationFoo(Application):
              schema_dict = {}
  
              @classmethod
              def name(cls):
                  return "foo"
  
          def register_plugin():
              return ApplicationFoo
  
      """
      def __init__(self):
          self.type_settings = config.plugins.application
          self.settings = self.type_settings.get(self.name())
  
      @classmethod
      def name(cls):
          """Return the name of the Application and rez-subcommand."""
          raise NotImplementedError
  
subject: add docstring