I think the `.batch_shape` should be equivalent to `.tensor.shape` or `.tensor.batch_shape` for graphs.

[saleml]

I think the .batch_shape should be equivalent to .tensor.shape or .tensor.batch_shape for graphs.
If so, why do we need this setter for the batch_shape?
My suggestion is:

@property
def batch_shape(self) -> tuple[int, ...]:
    return tuple(self.tensor.shape)[: -len(self.state_shape)]

Originally posted by @hyeok9855 in #252 (comment)

[josephdviviano]

I'm also not sure about this one.

[josephdviviano]

I disagree with my former self. I've implemented a fix that

• Does not permit the user to directly set the batch shape.
• Batch shape is mostly accessed from the underling tensor (in one case, we still use a self._batch_shape field.