PHPUnit - Check if an array contains an object of a specific type

While unit testing in PHPUnit, I'm in a situation where I need to check if an array contains al least one object of a specific type.

Here's a trivial example of what I'm looking for

$obj_1 = new Type1;
$obj_2 = new Type2; 

$container = array( $obj_1, $obj_2 );

// some logic and array manipulation here

// need something like this
$this->assertArrayHasObjectOfClass( 'Type1', $container );

Obviously I can do that with custom code, but is there any assertion (or combination of them) which allows me to do that?

I need to do that many times in multiple tests so, if the assertion I need doesn't esist, how do I extend the set of PHPUnit assertions?

EDIT: custom solution with trait

As suggested by Vail, I came up with a custom solution for this using traits. Here's a semplified version.

// trait code
trait CustomAssertTrait
{
    public function assertArrayHasObjectOfType( $type, $array, $message = '' ) {

        $found = false;

        foreach( $array as $obj ) {
            if( get_class( $obj ) === $type ) {
                $found = true;
                break;
            }
        }

        $this->assertTrue( $found, $message );

    }
}

// test code
class CustomTest extends PHPUnit_Framework_TestCase {
   use CustomAssertTrait;

   // test methods... 
}