python tornado中使用parse_command_line(final=False) final有何作用？

通过这样，找到源代码，请自己看方法文档

If final is False, parse callbacks will not be run.

This is useful for applications that wish to combine configurations
from multiple sources.

def parse_command_line(self, args=None, final=True):
        """Parses all options given on the command line (defaults to
        `sys.argv`).

        Note that ``args[0]`` is ignored since it is the program name
        in `sys.argv`.

        We return a list of all arguments that are not parsed as options.

        If ``final`` is ``False``, parse callbacks will not be run.
        This is useful for applications that wish to combine configurations
        from multiple sources.
        """
        if args is None:
            args = sys.argv
        remaining = []
        for i in range(1, len(args)):
            # All things after the last option are command line arguments
            if not args[i].startswith("-"):
                remaining = args[i:]
                break
            if args[i] == "--":
                remaining = args[i + 1:]
                break
            arg = args[i].lstrip("-")
            name, equals, value = arg.partition("=")
            name = self._normalize_name(name)
            if name not in self._options:
                self.print_help()
                raise Error('Unrecognized command line option: %r' % name)
            option = self._options[name]
            if not equals:
                if option.type == bool:
                    value = "true"
                else:
                    raise Error('Option %r requires a value' % name)
            option.parse(value)

        if final:
            self.run_parse_callbacks()

        return remaining