class_docstr: A dictionary that merges built-in and custom symbolic functions.
  
  It supports overriding and un-overriding built-in symbolic functions with custom
  ones.
code: def __len__(self) -> int:
      return len(self._merged)
  
imports: import warnings
  from typing import Callable, Collection, Dict, Generic, Optional, Sequence, Set, TypeVar, Union
  from torch.onnx import _constants, errors
  from torch.onnx._internal import _beartype
label_desc: Use image node_id 11 for calling the OverrideDict obj's underlying member method code with example usage: obj.__len__() and returns: len