code: def get_token(self):
          
          token = None
          try:
              doc = self.doc_ref.get()
          except Exception as e:
              log.error('Token (collection: {}, doc_id: {}) '
                        'could not be retrieved from the backend: {}'
                        .format(self.collection, self.doc_id, str(e)))
              doc = None
          if doc and doc.exists:
              token_str = doc.get(self.field_name)
              if token_str:
                  token = self.token_constructor(self.serializer.loads(token_str))
          self.token = token
          return token
docs: Retrieves the token from the store
          :return dict or None: The token if exists, None otherwise