>>> a = ts.Spec({'driver': 'n5', 'kvstore': {'driver': 'memory'}})
>>> b = a.copy()
>>> a.update(dtype=ts.uint8)
>>> b.update(dtype=ts.uint16)
>>> a
Spec({'driver': 'n5', 'dtype': 'uint8', 'kvstore': {'driver': 'memory'}})
>>> b
Spec({'driver': 'n5', 'dtype': 'uint16', 'kvstore': {'driver': 'memory'}})