title: lemmatize words in nest list
body: <p>How do I lemmatize words in the nested list in a single line? I tried few things, I am getting close but I think I may be getting syntax wrong? How do I fix it?</p>
  <pre><code>from nltk.stem import WordNetLemmatizer 
  lemmatizer = WordNetLemmatizer()
  word_list = [['test','exams','projects'],['math','exam','things']]
  word_list # type list
  
  Try #1: Does the lemmatization but in different format
  for word in word_list:
      for e in word: 
          print(lemmatizer.lemmatize(e)) # not the result I need for 
  
  Try #2: Looking for similar approach in one line to solve the problem. Not giving correct results. 
  [[word for word in lemmatizer.lemmatize(str(doc))] for doc in word_list]
  
  Output needed: 
  
  [['test','exam','project'],['math','exam','thing']]
  </code></pre>