class_docstr: Container with mappings shared across TraceTypes for placeholder values.
code: def add_placeholder(
      self, alias_id: Hashable, placeholder: Hashable
  ) -> None:
      if alias_id in self._alias_id_to_placeholder:
          raise KeyError(
              f"alias id: {alias_id} is already stored in this "
              "instance of placeholder context."
          )
      self._alias_id_to_placeholder[alias_id] = placeholder
  
imports: import collections.abc
  from typing import Any, Dict, Hashable, Optional
  import weakref
  from tensorflow.core.function.trace_type import custom_nest_trace_type
  from tensorflow.core.function.trace_type import default_types
  from tensorflow.core.function.trace_type import util
  from tensorflow.python.types import trace
  from tensorflow.python.util import custom_nest_protocol
label_desc: Use image node_id 4 for calling the InternalPlaceholderContext obj's underlying member method code with example usage: obj.add_placeholder(alias_id, placeholder) without return types