title: NameError: name 'wordnet' is not defined
body: <p>I'm trying to run this piece of code for synonym-based text augmentation.</p>
  <pre><code>import nlpaug.augmenter.char as nac
  import nlpaug.augmenter.word as naw
  import nlpaug.augmenter.sentence as nas
  import nlpaug.flow as nafc
  
  from nlpaug.util import Action
  
  text = 'The quick brown fox jumps over the lazy dog .'
  
  aug = naw.SynonymAug(aug_src='wordnet')
  augmented_text = aug.augment(text)
  </code></pre>
  <p>Getting this exception</p>
  <pre><code>---------------------------------------------------------------------------
  NameError                                 Traceback (most recent call last)
  &lt;ipython-input-30-9e2190c38612&gt; in &lt;module&gt;
  ----&gt; 1 aug = naw.SynonymAug(aug_src='wordnet')
        2 augmented_text = aug.augment(text)
  
  /anaconda/envs/azureml_py36/lib/python3.6/site-packages/nlpaug/augmenter/word/synonym.py in     __init__(self, aug_src, model_path, name, aug_min, aug_max, aug_p, lang, stopwords, tokenizer,     reverse_tokenizer, stopwords_regex, force_reload, verbose)
       62         self.model_path = model_path
       63         self.lang = lang
  ---&gt; 64         self.model = self.get_model(aug_src, lang, model_path, force_reload)
       65 
       66     def skip_aug(self, token_idxes, tokens):
  
  /anaconda/envs/azureml_py36/lib/python3.6/site-packages/nlpaug/augmenter/word/synonym.py in     get_model(cls, aug_src, lang, dict_path, force_reload)
      136     def get_model(cls, aug_src, lang, dict_path, force_reload):
      137         if aug_src == 'wordnet':
  --&gt; 138             return nmw.WordNet(lang=lang, is_synonym=True)
      139         elif aug_src == 'ppdb':
      140             return init_ppdb_model(dict_path=dict_path, force_reload=force_reload)
  
  /anaconda/envs/azureml_py36/lib/python3.6/site-packages/nlpaug/model/word_dict/wordnet.py in     __init__(self, lang, is_synonym)
       31             nltk.download('averaged_perceptron_tagger')
       32 
  ---&gt; 33         self.model = self.read()
       34 
       35     def read(self):
  
  /anaconda/envs/azureml_py36/lib/python3.6/site-packages/nlpaug/model/word_dict/wordnet.py in read    (self)
       34 
       35     def read(self):
  ---&gt; 36         return wordnet
       37 
       38     def predict(self, word, pos=None):
  
  NameError: name 'wordnet' is not defined
  </code></pre>
  <p>I've installed <code>nltk</code> and downloaded <code>wordnet</code> but got same error.</p>