$reflectionClass = new \ReflectionClass(MyClass::class);

$attributeReader = new Flexic\Attributes\Reader();

$attributeReader->getAttributes($reflectionClass); // Returns list of given attributes
$attributeReader->getAttribute($reflectionClass, MyAttribute::class); // Returns first attribute of given type
$attributeReader->hasAttribute($reflectionClass, MyAttribute::class); // Checks if attribute is defined on class.
$attributeReader->findClassesWithAttribute(MyAttribute::class); // Get all classes where Attribute is defined.