def cluster_idx_to_label_list(clusters, nr_journeys):
    """
    Transforms the cluster type output of PyClustering to the required list of labels needed 
    for scikit-learn operations.
    
    Parameters:
    -------------
        clusters: [list of lists] with object indices per cluster
    
    Returns:
        A list of predicted cluster labels 
    
    """
    labels = [None] * nr_journeys
    for label, cluster in enumerate(clusters):
        for idx in cluster:
            labels[idx] = label
    return labels