fix bug from #411

Author: wannaphong

pythainlp/tokenize/newmm.py

@@ -8,7 +8,6 @@
 from marisa_trie import Trie
 from collections import Counter, defaultdict
 from pythainlp.corpus.thaiword import get_data
-import string as str
 class LatticeString(str):
     def __new__(cls, value, multi=None, in_dict=True): 
         ''' Return a string instance