MathPHP\SetTheory\Set::isMember PHP Méthode

    public function isMember($x) : bool
    {
        return array_key_exists($this->getKey($x), $this->A);
    }

 /**
  * @dataProvider dataProviderForSingleSet
  */
 public function testIsMember(array $members)
 {
     $set = new Set($members);
     foreach ($members as $member) {
         $this->assertTrue($set->isMember($member));
     }
 }