You have to use this call in your constructor and after creating object just call the function something link this:
In your model file where you want to callcreateSubscriptions() write something like this
use NameSpace/Modulename/Model/Quote/SubscriptionCreator
private $subscriptionCreator;
then
public function __construct( SubscriptionCreator $subscriptionCreator
) {
$this->subscriptionCreator = $subscriptionCreator;
}
Now in which ever method you want to call createSubscriptions() you can call like this
$this->subscriptionCreator->createSubscriptions($quote,$order)
Note: For this module id there is any interface available than use interface.
For reference you can also have a look on this
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