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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 register_entry(self, navbar_kwargs):
 """Register a navbar entry with the copilot. Args: navbar_kwargs (dict):
 Arguments passed to the :class:`NavbarEntry` instance. """

        # Add a new rule for each level in the path.
        path = navbar_kwargs.pop('path')
        # If a single object is used rather than an iterable (including
        # a single string), wrap it before using.
        if not hasattr(path, '__iter__') or isinstance(path, basestring):
            path = [path]

        entry_group = self.navbar_entries
        # HACK: I'd like to intelligently replace the URL rule in the
        # case where the intended rule is provided, but the function has
        # already created a blank "placeholder" rule for it. There are
        # probably nicer ways to approach this, but it works.
        for name, is_last in iter_islast(path):
            kwargs = deepcopy(navbar_kwargs)
            kwargs['name'] = name
            for existing_entry in entry_group:
                # If there's an existing entry for this "link", use it
                # instead of creating a new one. If this existing entry
                # has no rule and this is the last item in ``path``, the
                # rule was intended to be assigned to this entry, so
                # overwrite the blank rule with the one provided via
                # ``navbar_kwargs``.
                if existing_entry.name == name:
                    entry = existing_entry
                    if is_last:
                        entry.endpoint = kwargs['endpoint']
                    break
            else:
                # If we can't find an existing entry, create one with a
                # blank endpoint. If this rule is not the final one in
                # the list, the endpoint was not intended for this, so
                # don't assign it.
                if not is_last:
                    kwargs['endpoint'] = None
                entry = NavbarEntry(**kwargs)
                entry_group.add(entry)
            entry_group = entry.children