# 预先加载NLTK语料库以避免多线程环境中的竞争条件
import nltk

load_flag = False


def load_nltk():
  global load_flag
  if not load_flag:
    nltk.download('punkt')
    nltk.download('averaged_perceptron_tagger')
    nltk.download('maxent_ne_chunker')
    nltk.download('words')
    load_flag = True