'Tests whether an element, other, is in the set.
Relies on Python\'s set class. This tests for object equality
All inputs are sympified
Examples
>>> from sympy import FiniteSet
>>> 1 in FiniteSet(1, 2)
True
>>> 5 in FiniteSet(1, 2)
False'

def _contains(self, other):

    r = false
    for e in self._elements:
        t = Eq(e, other, evaluate=True)
        if isinstance(t, Eq):
            t = t.simplify()
        if (t == true):
            return t
        elif (t != false):
            r = None
    return r
