def __init__(self, groups=None):
        super(GroupedRequirements, self).__init__(NamedRequirements)
        self.groups = groups or self.default_groups
        self.filename = None
        self.create_default_groups()
def get_clusters(self):
        """!
        @return (list) Allocated clusters where each cluster is represented by list of indexes of points from dataset,
                        for example, two cluster may have following representation [[0, 1, 4], [2, 3, 5, 6]].