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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def walk_commands(self):
 """An iterator that recursively walks through this cog's commands and subcommands."""

        from .core import GroupMixin
        for command in self.__cog_commands__:
            if command.parent is None:
                yield command
                if isinstance(command, GroupMixin):
                    yield from command.walk_commands()