'new binary sees (none, sees-f1)': ok
'new binary knows (knows-f0, none)': ok
'term 7': '7'
'term z': z
'term sees-f1 (7)': <sees-f1(*1) : '7'>
'term knows-f0 (sees-f1 (x))': <knows-f0(*1) : <sees-f1(*1) : x>>
'constant underlying 7': '7'
'constant underlying y': --
'constant underlying sees-f1 (7)': '7'
'variable underlying 7': --
'variable underlying y': y
'variable underlying knows-f0 (sees-f1 (x))': x