Replacing feed_dict in TF2.0 for tensor inputs to tensors in a function

I have a Keras Callback that retrieves values from particular Keras layers like so:

def run(self, fetches, next_batch):
    """Run fetches using the validation data passed in during initialization."""
    input_data, target_data = self.sess.run(next_batch)
    feed_dict = {self.model.inputs[0]: input_data,
                 self.model._targets[0]: target_data}
    result = self.sess.run(fetches=fetches, feed_dict=feed_dict)
    return result

next_batch was a Dataset.make_one_shot_iterator.get_next() call in tf1. I've replaced it with next(iter(ds)). That part works fine.

However I cannot figure out how to rewrite the sess.run() call. I want to get output from the 'fetches' tensors, but their inputs are other tensors higher up in the Model. I know which tensors are my input tensors, but how do I pass data into them and get the outputs I want from the tensors in later layers?

I read the conversion documentation on this subject but it is REALLY terse and unhelpful. I was not able to find much more information on stackoverflow.