code: def placeholder_value(self, placeholder_context=None):
      raise NotImplementedError
  
imports: from typing import Optional
  from tensorflow.core.function.polymorphism import function_type
  from tensorflow.core.function.polymorphism import type_dispatch
  from tensorflow.python.platform import test
  from tensorflow.python.types import trace
label_desc: Use image node_id 4 for calling the MockShape obj's underlying member method code with example usage: obj.placeholder_value(placeholder_context) without return types