def get_groups(self, query=None, exclude=None, limit=20):
        """
        REST endpoint for searching groups in a group picker
        Returns groups with substrings matching a given query. This is mainly for use with the group picker,
        so the returned groups contain html to be used as picker suggestions. The groups are also wrapped
        in a single response object that also contains a header for use in the picker,
        specifically Showing X of Y matching groups.
        The number of groups returned is limited by the system property "jira.ajax.autocomplete.limit"
        The groups will be unique and sorted.
        :param query: str
        :param exclude: str
        :param limit: int
        :return: Returned even if no groups match the given substring
        """
        url = 'rest/api/2/groups/picker'
        params = {}
        if query:
            params['query'] = query
        else:
            params['query'] = ''
        if exclude:
            params['exclude'] = exclude
        if limit:
            params['maxResults'] = limit
        return self.get(url, params=params)