old_contents: from pymongo import MongoClient
  from gensim import corpora, models, similarities
  import gensim
  
  db = MongoClient().articles.entries
  
  lda = gensim.models.LdaModel.load('data/lda_model')
  dic = gensim.corpora.Dictionary.load_from_text('data/wiki_en_wordids.txt')
  
  def entry2bow(entry):
      return dic.doc2bow(entry['text'].lower().split())
      
  def bow2topics(bow):
      return lda[bow]
  
  def entry2topics(entry):
      return bow2topics(entry2bow(entry))
      
  
new_contents: from pymongo import MongoClient
  from gensim import corpora, models, similarities
  import gensim
  
  db = MongoClient().articles.entries
  
  lda = gensim.models.LdaModel.load('data/lda400')
  dic = gensim.corpora.Dictionary.load_from_text('data/wiki_en_wordids.txt')
  
  def entry2bow(entry):
      return dic.doc2bow(entry['text'].lower().split())
      
  def bow2topics(bow):
      return lda[bow]
  
  def entry2topics(entry):
      return bow2topics(entry2bow(entry))
      
  
subject: use big lda