class_docstr: A base class for callback objects associated with Bokeh Documents
  and Sessions.
class_docstr_tok: ["A","base","class","for","callback","objects","associated","with","Bokeh","Documents","and","Sessions","."]
docstr: The callable that this callback wraps.
  
          
docstr_tok: ["The","callable","that","this","callback","wraps","."]
code: def callback(self) -> Callback:
      """The callable that this callback wraps."""
      return self._callback
  
imports: from __future__ import annotations
  import logging
  from typing import TYPE_CHECKING, Callable, Sequence
  from ..core.types import ID
  from ..util.tornado import _CallbackGroup
label_desc: Use image node_id 3 for calling the SessionCallback obj's underlying member method code with example usage: obj.callback() and returns: self