def valid_ids(nb_a, nb_b):
    """
    Ensure each notebook we are comparing has a full set of unique cell ids
    
    nb_a: (dict) one notebook to compare
    nb_b: (dict) the other notebook to compare
    """
    prior_a_ids = []
    prior_b_ids = []
    for c in nb_a:
        if 'comet_cell_id' not in c['metadata']:
            return False
        elif c['metadata']['comet_cell_id'] in prior_a_ids:
            return False
        else:
            prior_a_ids.append(c['metadata']['comet_cell_id'])
    for c in nb_b:
        if 'comet_cell_id' not in c['metadata']:
            return False
        elif c['metadata']['comet_cell_id'] in prior_b_ids:
            return False
        else:
            prior_b_ids.append(c['metadata']['comet_cell_id'])
    return True
