>>> schema = ts.Schema()
>>> print(schema.domain)
None
>>> schema.update(domain=ts.IndexDomain(labels=['x', 'y', 'z']))
>>> schema.update(domain=ts.IndexDomain(shape=[100, 200, 300]))
>>> schema.domain
{ "x": [0, 100), "y": [0, 200), "z": [0, 300) }