code: def setUp(self):
      super().setUp()
      self._space = gym.spaces.MultiDiscrete(nvec=[2, 2])
      self._serializer = space_serializer.create(
          self._space, vocab_size=2
      )
  
imports: import gin
  import gym
  import numpy
  from tensorflow import test
  from trax.rl import space_serializer
label_desc: Use image node_id 1 for calling the MultiDiscreteSpaceSerializerTest obj's underlying member method code with example usage: obj.setUp() without return types