code: def testRefDtype(self):
      with context.graph_mode(), self.cached_session():
          x = gen_state_ops.variable(shape=[1], dtype=dtypes.float32)
          result = math_ops.cast(x, dtypes.float32)
          self.assertEqual(x.dtype, dtypes.float32_ref)
          self.assertEqual(result.dtype, dtypes.float32)
  
imports: import numpy
  from tensorflow.python.eager import context
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import sparse_tensor
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import gen_state_ops
  from tensorflow.python.ops import gradient_checker_v2
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import variables
  from tensorflow.python.platform import test
label_desc: Use image node_id 18 for calling the CastOpTest obj's underlying member method code with example usage: obj.testRefDtype() without return types