def _remove_singular_obs(clusters):
    """Removes clusters with a singular observation."""
    new_cluster_index = 0
    multiobs_clusters = {}
    for _, cluster in clusters.items():
        if sum(map(len, cluster.values())) > 1:
            multiobs_clusters[new_cluster_index] = cluster
            new_cluster_index += 1
        else:
            print('Removed cluster with singular observation: {}'.format(
                cluster))
    return multiobs_clusters
