#Allows empty
acl
advcl
advmod
amod
appos
aux
case
cc
ccomp
clf
compound
conj
cop
csubj
dep
det
discourse
dislocated
expl
fixed
flat
goeswith
iobj
list
mark
nmod
nsubj
nummod
obj
obl
orphan
parataxis
punct
reparandum
root
vocative
xcomp
