import argparse

# argparse help error: arguments created by add_mutually_exclusive_group() are shown outside their parent group created by add_argument_group()
# prelimiary fix to the function that copies a parent parser to child

def new_container_add(self, container):
    # collect groups by titles
    title_group_map = {}
    for group in self._action_groups:
        if group.title in title_group_map:
            msg = _('cannot merge actions - two groups are named %r')
            raise ValueError(msg % (group.title))
        title_group_map[group.title] = group

    # map each action to its group
    group_map = {}
    for group in container._action_groups:

        # if a group with the title exists, use that, otherwise
        # create a new group matching the container's group
        if group.title not in title_group_map:
            title_group_map[group.title] = self.add_argument_group(
                title=group.title,
                description=group.description,
                conflict_handler=group.conflict_handler)

        # map the actions to their new group
        for action in group._group_actions:
            group_map[action] = title_group_map[group.title]

    # add container's mutually exclusive groups
    # NOTE: if add_mutually_exclusive_group ever gains title= and
    # description= then this code will need to be expanded as above
    for group in container._mutually_exclusive_groups:
        #print('container title',group._container.title)
        mutex_group = self.add_mutually_exclusive_group(
            required=group.required)

        # correct the _container attribute of the copied group
        mx_container = title_group_map[group._container.title]  #####
        mutex_group._container = mx_container                   #####

        # map the actions to their new mutex group
        for action in group._group_actions:
            group_map[action] = mutex_group

    # add all actions to this container or their group
    for action in container._actions:
        group_map.get(action, self)._add_action(action)

argparse._ActionsContainer._add_container_actions = new_container_add

# create parent parser
parent_parser = argparse.ArgumentParser(add_help = False)
# create group for its arguments
global_group = parent_parser.add_argument_group("global arguments")
global_group.add_argument("--global-arg1")
global_group.add_argument("--global-arg2")
mutex_group = global_group.add_mutually_exclusive_group()
mutex_group.add_argument("--mutex-arg1")
mutex_group.add_argument("--mutex-arg2")
# create child parser
child_parser = argparse.ArgumentParser(parents = [parent_parser])
child_parser.add_argument("--child-arg1")
child_parser.add_argument("--child-arg2")
print("="*100)
parent_parser.print_help()
print("="*100)
child_parser.print_help()