code: @Override
      public <Instance> void removeInstance(Instance instance) {
          DatastoreType datastoreType = getDatastoreType(instance);
          DatastoreId id = getDatastoreId(datastoreType);
          cache.remove(id);
      }
docs: Removes an instance, e.g. before deletion or migration.
  
  @param instance
  The instance.
  @param <Instance>
  The instance type.