code: def _is_iso8601(candidate_str):
      ISO8601 = r"^\d{4}-\d{2}-\d{2}[ T]\d{2}:\d{2}:\d{2}\.\d{6}$"
      return re.compile(ISO8601).match(candidate_str) is not None
  
imports: import json
  import os.path
  import re
  import warnings
  from collections import Counter, OrderedDict
  from collections.abc import Iterable
  from copy import deepcopy
  from datetime import datetime, timedelta, timezone
  from itertools import takewhile
  from textwrap import shorten
  import numpy
  from scipy.io import loadmat
  from ._fiff.constants import FIFF
  from ._fiff.open import fiff_open
  from ._fiff.tag import read_tag
  from ._fiff.tree import dir_tree_find
  from ._fiff.write import _safe_name_list, end_block, start_and_end_file, start_block, write_double, write_float, write_name_list_sanitized, write_string
  from .utils import _check_dict_keys, _check_dt, _check_fname, _check_option, _check_pandas_installed, _check_time_format, _convert_times, _DefaultEventParser, _dt_to_stamp, _is_numeric, _mask_to_onsets_offsets, _on_missing, _pl, _stamp_to_dt, _validate_type, check_fname, fill_doc, int_like, logger, verbose, warn
label_desc: Use image node_id 13 for calling a global function with example usage: _is_iso8601(candidate_str) and returns: unknown