def METHOD_NAME(self):
    """Find all groups in dataset and which group each line belongs."""
    line_groups_ids = []
    groups_ids = set()
    lines = self._line_reader.lines_generator()
    # Need to return group id of line and line as string.
    for group_id, _ in lines:
        line_groups_ids.append(group_id)
        groups_ids.add(group_id)
    return line_groups_ids, groups_ids