code: def list_credentials(self, user=None):
          
          if not user:
              user = self.user
          user_id = utils.get_id(user)
          uri = "users/%s/OS-KSADM/credentials" % user_id
          resp, resp_body = self.method_get(uri)
          return resp_body.get("credentials")
docs: Returns a user's non-password credentials. If no user is specified, the
          credentials for the currently authenticated user are returned.
  
          You cannot retrieve passwords by this or any other means.