'Check for logical equivalence.
Pass the expression (self <-> other) to the theorem prover.
If the prover says it is valid, then the self and other are equal.
:param other: an ``DrtExpression`` to check equality against
:param prover: a ``nltk.inference.api.Prover``'

def equiv(self, other, prover=None):

    assert isinstance(other, DrtExpression)
    f1 = self.simplify().fol()
    f2 = other.simplify().fol()
    return f1.equiv(f2, prover)
