It shows how to enqueue examples and feed them through the NER model, for annotation.
For your second question, do you simply want the metadata to be displayed to the annotator? You can do that by adding a meta key to the examples, e.g. {"text": "some text", "meta": {"key": "value"}}. This won’t use the metadata as a feature in the model, though. There’s not really a good way to do that currently.