Oliver Beckstein

@sperezconesa development on MDSynthesis has largely halted – @dotsdl is not really maintaining it anymore. Instead we suggest to used datreant directly. MDSynthesis was a good idea but it turned...

Pickling universes is a hard problem, see https://github.com/MDAnalysis/mdanalysis/issues/878 (and a whole bunch of [somewhat related issues](https://github.com/MDAnalysis/mdanalysis/issues?q=is%3Aissue+pickle+universe+is%3Aopen)) so it does not work yet in MDAnalysis. (But we would *really* like it...

The lines in the MDS code https://github.com/datreant/MDSynthesis/blob/980e9dd4d8b8df076b621a9a391be6179112dc40/src/mdsynthesis/treants.py#L89-L109

oops... Will merge when tests are ✅

ping @hmacdope @ljwoods2

@edisj @ljwoods2 is this issue a known limitation in our H5MD implementation?

@PythonFZ how would you expect MDAnalysis to support groups, i.e., what exactly should be happening?

I could reproduce with ```python import MDAnalysis as mda import numpy as np u = mda.Universe.empty(100, n_residues=100, atom_resindex=np.arange(100), trajectory=True) u.load_new("licl_100.h5", format="H5MD", convert_units=False) ``` and failed with ``` KeyError: "Unable to...

yes — it's mandatory

[Observables in H5MD](https://www.nongnu.org/h5md/h5md.html#observables-group). Let's assume we have the below: ``` observables \-- | \-- step: Integer[variable] | \-- time: Float[variable] | \-- value: [variable] \-- | \-- step: Integer[variable] |...