For example, "北/north/B_NR", "京/capital/M_NR", and "市/city/E_NR" will be merged as "北京市 /Beijing/NR", "是/is/S_VC" will become "是 /is/VC".
if no constituent in the parse tree can map the same text span to an argument in the manual annotation, the system will not get a correct annotation.