'Return the truth value of the condition.'

@classmethod
def __eval_cond(cls, cond):

    from sympy.solvers.solvers import checksol
    if (cond == True):
        return True
    if isinstance(cond, Equality):
        diff = (cond.lhs - cond.rhs)
        if diff.is_commutative:
            return diff.is_zero
    return None
