BackendEntrypoint bug chunking data

What happened?

Hi together,
I have written a class for the BackendEntrypoint. Since the data can be quite large, I wrote huge parts by making use of the dask.delayed function. As one of the last steps I am redefining the chunks. The code is loading single files and concatenates them into a xarray. As a result, it makes sense to chunk for each single file. This chunking is not forwarded to the main program, where the class is used:
dset = dset.chunk(dict(zip(dims, list(reversed([list(reversed(list(shape)))[i] if i < 4 else 1 for i in range(len(list(shape)))])))))
return dset
https://github.com/timvgl/mumaxXR/blob/daa4345b482197b65a7bd88df1552d9fa48b8bf7/src/mumaxXR/OvfEngine.py#L356-L357
Between dset = .... and return dset dset.chunksizes gives the expcted values. However, in the main program, the chunking is not available anymore and dset.chunksizes gives Frozen({}).
Thanks for your help!
Tim

What did you expect to happen?

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Minimal Complete Verifiable Example

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MVCE confirmation

• Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• Complete example — the example is self-contained, including all data and the text of any traceback.
• Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• New issue — a search of GitHub Issues suggests this is not a duplicate.
• Recent environment — the issue occurs with the latest version of xarray and its dependencies.

Relevant log output

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Anything else we need to know?

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Environment

xarray version: 2023.1.0
Linux

Inspect src/mumaxXR/OvfEngine.py at lines 356-357 and compare dset.chunksizes before returning from BackendEntrypoint with the value seen in the main program. Reproduce the transition using the reported dask.delayed and file-concatenation flow, then establish why the chunk metadata is lost and verify that the expected chunking remains available to the caller.