code: def save_token(self):
          
          if self.token is None:
              raise ValueError('You have to set the "token" first.')
  
          try:
              # set token will overwrite previous data
              self.doc_ref.set({
                  self.field_name: self.serializer.dumps(self.token)
              })
          except Exception as e:
              log.error('Token could not be saved: {}'.format(str(e)))
              return False
  
          return True
docs: Saves the token dict in the store
          :return bool: Success / Failure