code: def testString(self):
      data = array_ops_stack.stack([b"data"])
      buffer_var = variable_v1.VariableV1(
          initial_value=array_ops.zeros(shape=(), dtype=dtypes.string),
          trainable=False,
          collections=[ops.GraphKeys.LOCAL_VARIABLES],
          name="buffer",
          dtype=dtypes.string,
          validate_shape=False,
          use_resource=False,
      )
      result = state_ops.assign(buffer_var, data, validate_shape=False)
      with self.cached_session() as sess:
          sess.run(variables.local_variables_initializer())
          self.assertEqual(result.eval(), b"data")
  
imports: import numpy
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import errors
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import tensor_shape
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import array_ops_stack
  from tensorflow.python.ops import gen_state_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import state_ops
  from tensorflow.python.ops import variable_v1
  from tensorflow.python.ops import variables
  from tensorflow.python.platform import test
label_desc: Use image node_id 26 for calling the VariableOpTest obj's underlying member method code with example usage: obj.testString() without return types