class_docstr: Common tests for noisy mixture distributions.
code: def test_can_instantiate_scalar(self):
      dist = self.dist_cls(
          loc=[3.0, -3.0], scale=[5.0, 2.5], weight=[0.3, 0.7]
      )
      self.assertEqual(dist.batch_shape, ())
      self.assertEqual(dist.event_shape, ())
  
imports: import tensorflow
  from tensorflow_compression.python.distributions import helpers
  from tensorflow_compression.python.distributions import uniform_noise
label_desc: Use image node_id 1 for calling the MixtureTest obj's underlying member method code with example usage: obj.test_can_instantiate_scalar() without return types