code: def testMultipleRegistration(self):
      @registry.register_optimizer
      def my_optimizer(learning_rate, hparams):
          return 3
  
      with self.assertRaisesRegexp(KeyError, "already registered"):
  
          @registry.register_optimizer("my_optimizer")
          def another_fn(learning_rate, hparams):
              return 5
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from tensor2tensor.utils import registry
  from tensor2tensor.utils import t2t_model
  import tensorflow.compat.v1
label_desc: Use image node_id 5 for calling the OptimizerRegistryTest obj's underlying member method code with example usage: obj.testMultipleRegistration() and returns: int, int