['they', 'detect', 'sign', 'EmptyParameter', 'EmptyParameter']
['<PRP>', 'see-30.1-1-1', "Synset('artifact.n.01')", 'EmptyParameter', 'EmptyParameter']
They can not detect any life signs.
<PRP> can not detect any Synset('record.n.01') Synset('artifact.n.01').