Use Variable.array instead of Variable.data

[muupan]

Since Chainer v3, chainer.Variable has the array property that is equivalent to the data property. It is better to use array because it can catch a bug of unintentionally accessing numpy.ndarray.data.

https://docs.chainer.org/en/stable/reference/generated/chainer.Variable.html#chainer.Variable.data

Note that using this attribute directly is discouraged; use array instead. Using array, you can find an error earlier when your code mixes up Variable and ndarray because ndarray does not have an attribute .array while it has .data.

[muupan]

I noticed that there appears some code that use .data again.