code: def test_user_type_fails(self, r):
      class Foo:
          def __str__(self):
              return "Foo"
  
      with pytest.raises(redis.DataError):
          r.set("a", Foo())
  
imports: import pytest
  import redis
  from redis.connection import Connection
  from redis.utils import HIREDIS_PACK_AVAILABLE
  from .conftest import _get_client
label_desc: Use image node_id 3 for calling the TestInvalidUserInput obj's underlying member method code with example usage: obj.test_user_type_fails(r) and returns: str