code: def _union_all(iterables):
      """Union entries in ``iterables`` into a set."""
      return set().union(*iterables)
  
imports: from contextlib import contextmanager
  from copy import deepcopy
  from itertools import product
  import operator
  import warnings
  import numpy
  import pandas
  from distutils.version import StrictVersion
  from trading_calendars.utils.pandas_utils import days_at_time
label_desc: Use image node_id 12 for calling a global function with example usage: _union_all(iterables) and returns: set