def vm_to_mm(verbal_model):
    """ Convert VM to MM. Time information will be lost.

    >>> a = VerbalModels.Prop(name="a", neg=False, identifying=False, t=123)
    >>> non_b = VerbalModels.Prop(name="b", neg=True, identifying=False, t=456)
    >>> vm = [VerbalModels.Individual(props=[a], t=789), VerbalModels.Individual(props=[a, non_b], t=159)]
    >>> vm_to_mm(vm)
    [['a'], ['a', '-b']]
    """

    mental_model = []
    for i, ind in enumerate(verbal_model):
        mental_model.append([])
        for p in ind.props:
            p_str = "-"+p.name if p.neg else p.name
            mental_model[i].append(p_str)
    return [sorted(row, key=lambda e: e[-1]) for row in mental_model]