def readSEEDTree(treeFile):
    """
    Return nested dictionary where first dict is map from levels (1,2,3)
    and next dict is map from role to name.

    This is a simply formatted file with 4 columns:
    "role\tsubsystem\tlevel 2\t level 1"
    """
    seedTree = {'1': {}, '2': {}, '3': {}}
    with open(treeFile) as f:
        for line in f:
            (role, l3, l2, l1) = line.rstrip().split('\t')
            seedTree['1'][role] = l1
            seedTree['3'][role] = l3
            seedTree['2'][role] = l2
    return seedTree