docs: def json_description(shape, **metadata):
      """Return JSON image description from data shape and other metadata.
  
      Return UTF-8 encoded JSON.
  
      >>> json_description((256, 256, 3), axes='YXS')  # doctest: +SKIP
      b'{"shape": [256, 256, 3], "axes": "YXS"}'
  
      """
      metadata.update(shape=shape)
      return json.dumps(metadata)