With the change of source name for corrected data while maintaining backwards compatibility through the concept of legacy sources, this adds a correspondig call creating the soft links to DataFile.
with DataFile(p, 'w') as f:
f.create_index(train_ids)
instr_src = f.create_instrument_source('AN/ACTUAL/DEVICE:output')
instr_src.create_key('data.bar', np.random.rand(len(train_ids)))
instr_src.create_index(bar=np.ones(len(train_ids)))
f.create_legacy_source('A/LEGACY/DEVICE:xtdf', 'AN/ACTUAL/DEVICE:output')
f.create_metadata()(and pending CI)