title: Python Mendeley SDK API returns error in authentication
body: <p>I have a mendeley account which I am using from their online version. I created a userid and client secret, saved it in config.yml file from and using it to authenticate. I am using the below code available on <a href="https://mendeley-python.readthedocs.io/en/latest/usage.html#authentication" rel="nofollow noreferrer">their website</a></p>
  
  <pre><code>import yaml
  from mendeley import Mendeley
  
  with open('config.yml') as f:
      config = yaml.load(f)
  
  REDIRECT_URI = 'http://localhost:5000/oauth'
  
  mendeley = Mendeley(config['clientId'], config['clientSecret'], REDIRECT_URI)
  auth = mendeley.start_client_credentials_flow()
  session = auth.authenticate()
  </code></pre>
  
  <p>This code works fine and I got not errors. But when I am trying to access data using the commands in the <a href="https://mendeley-python.readthedocs.io/en/latest/usage.html#examples" rel="nofollow noreferrer">example</a> it throws error. For example </p>
  
  <pre><code>&gt;&gt; print (session.profiles.me.display_name)
  
  mendeley.exception.MendeleyApiException: The Mendeley API returned an error (status: 400, message: No userid found in auth token)
  
  &gt;&gt; for document in session.documents.iter():
      print document.title
  
  mendeley.exception.MendeleyApiException: The Mendeley API returned an error (status: 403, message: Access to this document is not allowed)
  </code></pre>
  
  <p>I am stuck here and do not know how to access the data or articles I have on mendeley fom its API. Any help will be highly appreciated.</p>