src/Logic/Not.php
public function equivalentTo(Expression $other)
    {
        // Since this class is final, we can check with instanceof
        return $other instanceof $this && $this->expr->equivalentTo($other->expr);
    }
public function equivalentTo(Expression $other)
    {
        // Since this class is final, we can check with instanceof
        return $other instanceof $this && $this->expr->equivalentTo($other->expr);
    }
{@inheritdoc}