code: def add_tenant_user_role(request, project=None, user=None, role=None,
                           group=None, domain=None):
      
      manager = keystoneclient(request, admin=True).roles
      if VERSIONS.active < 3:
          manager.add_user_role(user, role, project)
      else:
          manager.grant(role, user=user, project=project,
                        group=group, domain=domain)
docs: Adds a role for a user on a tenant.