'Find the Power set of \'self\'.
Examples
>>> from sympy import FiniteSet, EmptySet
>>> A = EmptySet()
>>> A.powerset()
{EmptySet()}
>>> A = FiniteSet(1, 2)
>>> a, b, c = FiniteSet(1), FiniteSet(2), FiniteSet(1, 2)
>>> A.powerset() == FiniteSet(a, b, c, EmptySet())
True
References
.. [1] http://en.wikipedia.org/wiki/Power_set'

def powerset(self):

    return self._eval_powerset()
