class_docstr: str subclass that returns itself in repr
code: def __repr__(self):  # pylint: disable=invalid-repr-returned
      return self
  
file_path: dgl/python/dgl/utils/exception.py
imports: import sys
  import traceback
label_desc: Use image node_id 1 for calling the KeyErrorMessage obj's underlying member method code with example usage: obj.__repr__() and returns: self