<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_path_argument(cls, group, argname, dest=None, help_=None):
 """ Subclasses may call this to expose a path argument. Args: group: arparse.ArgumentGroup, the extension argument group argname: str, the name of the argument, will be namespaced. dest: str, similar to the `dest` argument of `argparse.ArgumentParser.add_argument`, will be namespaced. help_: str, similar to the `help` argument of `argparse.ArgumentParser.add_argument`. """

        prefixed = '%s-%s' % (cls.argument_prefix, argname)
        if dest is None:
            dest = prefixed.replace('-', '_')
            final_dest = dest[len(cls.argument_prefix) + 1:]
        else:
            final_dest = dest
            dest = '%s_%s' % (cls.argument_prefix, dest)

        group.add_argument('--%s' % prefixed, action='store',
                           dest=dest, help=help_)
        cls.path_arguments[dest] = final_dest