tests/test_HDF5_recorder.py: Add `__getitem__` tests for current group.
tests/test_HDF5_recorder.py: Add `__getitem__` tests for current group.

DudLab/nanshe,jakirkham/nanshe,jakirkham/nanshe,nanshe-org/nanshe,DudLab/nanshe,nanshe-org/nanshe