class_docstr: Container for variables and flags shared across TraceType generation.
code: def get_placeholder_mapping(self) -> Dict[Hashable, Any]:
      return self._alias_id_to_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 InternalTracingContext obj's underlying member method code with example usage: obj.get_placeholder_mapping() and returns: self