['he', 'leave', 'search', 'EmptyParameter', 'EmptyParameter'] ['he', 'search', 'EmptyParameter', 'it', 'for']
['<PRP>', 'leave-51.2-1', 'search-35.2', 'EmptyParameter', 'EmptyParameter'] ['<PRP>', 'search-35.2', 'EmptyParameter', '<PRP>', 'for']
He leaves to search for it.
<PRP> leaves to search for <PRP>.