private void persist(Subscription[] requirements, SubscriptionRole subscriptionRole)
{
requirements.Each(x => {
x.NodeName = _graph.Name;
x.Role = subscriptionRole;
});
var existing = _persistence.LoadSubscriptions(_graph.Name, subscriptionRole);
var newReqs = requirements.Where(x => !existing.Contains(x)).ToArray();
newReqs.Each(x => x.Id = Guid.NewGuid());
_persistence.Persist(newReqs);
}