class_docstr: A container for all capture usages within FuncGraph.
code: def by_ref_external(self):
      return self._by_ref_external
  
imports: import collections
  import functools
  from typing import Any, Callable, Hashable, Mapping, Optional
  from tensorflow.core.function import trace_type
  from tensorflow.python import pywrap_tfe
  from tensorflow.python.framework import dtypes
  from tensorflow.python.types import core
  from tensorflow.python.util import object_identity
label_desc: Use image node_id 15 for calling the FunctionCaptures obj's underlying member method code with example usage: obj.by_ref_external() and returns: self