code: def doc2vec(self, doc):
          
          bow = self.dictionary.doc2bow(doc['tokens'])
          if self.method == 'lsi':
              return self.lsi[self.tfidf[bow]]
          elif self.method == 'lda':
              return self.lda[bow]
          elif self.method == 'lda_tfidf':
              return self.lda[self.tfidf[bow]]
          elif self.method == 'logentropy':
              return self.logent[bow]
docs: Convert a single SimilarityDocument to vector.