for now, using bounded-depth lightning bolts: infinite depth doesn't work yet: don't understand lazy sequences enough yet.
add test for lightningb at this point: makes specific quantity check (.size = 6), TODO: testing for a hard-wired quantity makes test brittle: quantity will change if parents set or lex set changes.
add (fops):  "show the phrase-structure of a feature structure, e.g [hh21 'mangiare (to eat)' [cc10 'il (the)' 'pane(bread)']]"