code: def verify_oauth_token_and_set_current_user():
      
      for func in oauth2._before_request_funcs:
          func()
  
      if not hasattr(request, 'oauth') or not request.oauth:
          scopes = []
          try:
              valid, req = oauth2.verify_request(scopes)
          except ValueError:
              abort(400, 'Error trying to decode a non urlencoded string.')
  
          for func in oauth2._after_request_funcs:
              valid, req = func(valid, req)
  
          if valid:
              request.oauth = req
docs: Verify OAuth token and set current user on request stack.
  
      This function should be used **only** on REST application.
  
      .. code-block:: python
  
          app.before_request(verify_oauth_token_and_set_current_user)