assert expected classifier response

iobber/chunker.py

@@ -227,6 +227,8 @@ class Chunker:
 							non_O_tag, non_O_chan = decsn_array
 						elif len(decsn_array) == 3:
 							non_O_tag, non_O_chan, is_head = decsn_array
+						else:
+							raise IOError('Unexpected label returned from classifier: ' + decsn)
 					for chan_name in chans:
 						chan = asent.get_channel(chan_name)
 						# TODO: rename the from_string in corpus2 and fix it here