['he', 'start', 'complain', 'EmptyParameter', 'EmptyParameter']
['<PRP>', 'begin-55.1', 'complain-37.8', 'EmptyParameter', 'EmptyParameter']
All of a sudden, he starts complaining of pain in his stomach.
all of a sudden, <PRP> starts complaining of Synset('perception.n.03') in <PRP> Synset('part.n.03').