docs: def get_initial(self):
          """
          Try to find a demo source for given mode if any, if finded use it to
          fill the demo textarea.
          """
          initial = {}
  
          if self.kwargs.get('mode', None):
              filename = "{}.txt".format(self.kwargs['mode'])
              filepath = os.path.join(settings.BASE_DIR, 'demo_datas', filename)
              if os.path.exists(filepath):
                  with io.open(filepath, 'r', encoding='utf-8') as fp:
                      initial['foo'] = fp.read()
  
          return initial