docs: def get_secret(self, handle, contributor):
          """Retrieve an existing secret's value.
  
          :param handle: Secret handle
          :param contributor: User instance to perform contributor validation,
              which means that only secrets for the given contributor will be
              looked up.
          """
          queryset = self.all()
          if contributor is not None:
              queryset = queryset.filter(contributor=contributor)
          secret = queryset.get(handle=handle)
          return secret.value