Acceptance tests for Array Object Semantics
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>>> import xchainer as xc

>>> a = xc.Array((3,), xc.float32, [1, 2, 3]).require_grad('graph1')
>>> grad = xc.ones((3,), xc.float32)
>>> a.set_grad(grad, 'graph1')
>>> a.get_grad('graph1') is grad
True

Add acceptance tests for changing array object semantics
Add acceptance tests for changing array object semantics
