您好，想咨询一下conlleval中end_of_chunk这类代码的含义，自己看了不是很明白

[mz2sj]

def end_of_chunk(prev_tag, tag, prev_type, type_):
# check if a chunk ended between the previous and current word
# arguments: previous and current chunk tags, previous and current types
chunk_end = False

if prev_tag == 'E': chunk_end = True
if prev_tag == 'S': chunk_end = True

if prev_tag == 'B' and tag == 'B': chunk_end = True
if prev_tag == 'B' and tag == 'S': chunk_end = True
if prev_tag == 'B' and tag == 'O': chunk_end = True
if prev_tag == 'I' and tag == 'B': chunk_end = True
if prev_tag == 'I' and tag == 'S': chunk_end = True
if prev_tag == 'I' and tag == 'O': chunk_end = True

if prev_tag != 'O' and prev_tag != '.' and prev_type != type_:
    chunk_end = True

# these chunks are assumed to have length 1
if prev_tag == ']': chunk_end = True
if prev_tag == '[': chunk_end = True

return chunk_end