title: Module 'pytextrank' has no attribute 'parse_doc'
body: <p>I am performing a nlp task. I have written the following code. While executing, it is showing the following error. Any suggestion to resolve the error will be helpful. I am having python 3 env in google colab .</p>
  
  <pre><code># Pytextrank
  import pytextrank
  import json
  
  # Sample text
  sample_text = 'I Like Flipkart. He likes Amazone. she likes Snapdeal. Flipkart and amazone is on top of google search.'
  
  # Create dictionary to feed into json file
  
  file_dic = {"id" : 0,"text" : sample_text}
  file_dic = json.dumps(file_dic)
  loaded_file_dic = json.loads(file_dic)
  
  # Create test.json and feed file_dic into it.
  with open('test.json', 'w') as outfile:
  json.dump(loaded_file_dic, outfile)
  
  path_stage0 = "test.json"
  path_stage1 = "o1.json"
  
  # Extract keyword using pytextrank
  with open(path_stage1, 'w') as f:
  for graf in pytextrank.parse_doc(pytextrank.json_iter(path_stage0)):
  f.write("%s\n" % pytextrank.pretty_print(graf._asdict()))
  
  print(pytextrank.pretty_print(graf._asdict()))
  </code></pre>
  
  <p>I am getting the following error :</p>
  
  <pre><code>  AttributeError                            Traceback (most recent call last)      
    &lt;ipython-input-33-286ce104df34&gt; in &lt;module&gt;()      
         20 # Extract keyword using pytextrank      
         21 with open(path_stage1, 'w') as f:      
    ---&gt; 22   for graf in 
    pytextrank.parse_doc(pytextrank.json_iter(path_stage0)):     
         23     f.write("%s\n" % pytextrank.pretty_print(graf._asdict()))       
         24     print(pytextrank.pretty_print(graf._asdict()))      
  
        AttributeError: module 'pytextrank' has no attribute 'parse_doc'   
  </code></pre>