def load_layer1_to_cdbg(cdbg_to_catlas, domfile):
    """Load the mapping between first layer catlas and the original DBG nodes."""
    layer1_to_cdbg = {}
    fp = open(domfile, 'rt')
    for line in fp:
        dom_node, *beneath = line.strip().split(' ')
        dom_node = int(dom_node)
        beneath = map(int, beneath)
        equiv_cdbg_to_catlas = cdbg_to_catlas[dom_node]
        layer1_to_cdbg[equiv_cdbg_to_catlas] = set(beneath)
    fp.close()
    return layer1_to_cdbg
