def _flatten_ntd(ntd):
    """
    Flatten a two level nested table dictionary.
    """
    flattened_ntd = dict()
    for assign_outer in ntd.keys():
        for assign_inner in ntd[assign_outer].keys():
            flattened_ntd[assign_outer + assign_inner] = ntd[assign_outer][assign_inner]
    return flattened_ntd