class_docstr: Test of base registry.Registry class.
class_docstr_tok: ["Test","of","base","registry.Registry","class","."]
code: def testNoKeyProvided(self):
      r = registry.Registry("test")
  
      def f():
          return 3
  
      r.register(f)
      self.assertEqual(r["f"](), 3)
  
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 3 for calling the RegistryClassTest obj's underlying member method code with example usage: obj.testNoKeyProvided() and returns: int