['he', 'observe', 'alien', 'year', 'for']
['<PRP>', 'investigate-35.4', "Synset('entrant.n.03')", '<DURATION>0', 'for']
He's been observing aliens for eight hundred years and hasn't been surprised yet.
He's been observing Synset('entrant.n.03') for <DURATION>0 and hasn't been Synset('surprised.a.01') yet.