class_docstr: Define the ``ERROR`` message for reporting error conditions back to a
  Bokeh server.
  
  The ``content`` fragment of for this message is has the form:
  
  .. code-block:: python
  
      {
          'text'      : <error message text>
  
          # this is optional
          'traceback' : <traceback text>
      }
class_docstr_tok: ["Define","the","``","ERROR","``","message","for","reporting","error","conditions","back","to","a","Bokeh","server",".","The","``","content","``","fragment","of","for","this","message","is","has","the","form",":","..","code-block",":",":","python","{","'text","'",":","<","error","message","text",">","#","this","is","optional","'traceback","'",":","<","traceback","text",">","}"]
code: def __repr__(self) -> str:
      msg = super().__repr__()
      msg += " --- "
      msg += self.content["text"]
      if self.content["traceback"] is not None:
          msg += "\n" + self.content["traceback"]
      return msg
  
file_path: bokeh/src/bokeh/protocol/messages/error.py
imports: from __future__ import annotations
  import logging
  import sys
  from traceback import format_exception
  from typing import Any, TypedDict
  from ...core.types import ID
  from ..message import Message
label_desc: Use image node_id 1 for calling the error obj's underlying member method code with example usage: obj.__repr__() and returns: msg