Returns a one dimension array with the Place where the points 
        belong.
        
        :returns: The ``pyny.Place`` where the points belong.
        :rtype: list of int

def get_sets_index(self):
        """
        Returns a one dimension array with the Place where the points 
        belong.
        
        :returns: The ``pyny.Place`` where the points belong.
        :rtype: list of int
        """
        index = []
        for i, place in enumerate(self):
            index.append(np.ones(place.set_of_points.shape[0])*i)
        return np.concatenate(index).astype(int)