code: @Override
      public <Instance> DatastoreType getDatastoreType(Instance instance) {
          InstanceInvocationHandler<DatastoreType> invocationHandler = proxyFactory.getInvocationHandler(instance);
          return invocationHandler.getDatastoreType();
      }
docs: Return the datastore type represented by an instance.
  
  @param instance
  The instance.
  @param <Instance>
  The instance type.
  @return The corresponding datastore type.