code: def is_no_update(obj):
      return isinstance(obj, NoUpdate) or (
          isinstance(obj, dict)
          and obj == {"_dash_no_update": "_dash_no_update"}
      )
  
file_path: dash/dash/_callback.py
imports: import collections
  import hashlib
  from functools import wraps
  import flask
  from .dependencies import handle_callback_args, handle_grouped_callback_args, Output
  from .exceptions import PreventUpdate, WildcardInLongCallback, MissingLongCallbackManagerError, LongCallbackError
  from ._grouping import flatten_grouping, make_grouping_by_index, grouping_len
  from ._utils import create_callback_id, stringify_id, to_json, coerce_to_list, AttributeDict, clean_property_name
  from .None import _validate
  from .long_callback.managers import BaseLongCallbackManager
  from ._callback_context import context_value
label_desc: Use image node_id 2 for calling the NoUpdate obj's underlying member method code with example usage: obj.is_no_update(obj) and returns: unknown