Blocks can be access with get_block(blockindex). This works for symmetric as well as for non-symmetric UniTensors. For the latter, the blockindex is not needed. But it can still be specified and is currently simply ignored. If a blockindex != 0 is given, the user seems to assume a block form, which is wrong.

I would suggest that there is a check: for a UniTensor which is not in block form, blockindex has to be either 0 or omitted. Otherwise there should be an error.

Python Example:

Create an UniTensor from Tensor

T = cytnx.UniTensor(cytnx.ones([3,3]))
print(T.get_block(2))

Should produce something like: [ERROR] Trying to access a block with blockindex != 0 on a UniTensor without block form!