udapi.core.mwt needs the .feats property, just like udapi.core.node

[dan-zeman]

Multiword tokens normally do not have features, unlike nodes. However, since UD guidelines amendment 8, they can have Typo=Yes. Therefore, the FEATS field should be read and preserved when processing a MWT line.

Context: This would be useful to have when resolving UniversalDependencies/tools#140

[martinpopel]

OK, I am going to add wmt.feats.

[dan-zeman]

Thanks!