def find_cluster_members(pdb, clusterings):
    """
    Find all other pdbs that co-occur in a cluster with a given pdb
    """
    pdb2cluster, cluster2pdb = clusterings
    clusters = pdb2cluster[pdb]
    all_pdbs = set()
    for clust in clusters:
        pdbs = cluster2pdb[clust]
        all_pdbs = all_pdbs.union(pdbs)
    return all_pdbs