'Return self as a dictionary of factors with each factor being
treated as a power. The keys are the bases of the factors and the
values, the corresponding exponents. The resulting dictionary should
be used with caution if the expression is a Mul and contains non-
commutative factors since the order that they appeared will be lost in
the dictionary.'

def as_powers_dict(self):

    d = defaultdict(int)
    d.update(dict([self.as_base_exp()]))
    return d
