code: def _check_stc_iterable(stc, info):
      # 1. Check that our STC is iterable (or convert it to one using cycle)
      # 2. Do first iter so we can get the vertex subselection
      # 3. Get the list of verts, which must stay the same across iterations
      if isinstance(stc, _BaseSourceEstimate):
          stc = [stc]
      _validate_type(
          stc, Iterable, "SourceEstimate, tuple, or iterable"
      )
      stc_enum = enumerate(stc)
      del stc
  
      try:
          stc_counted = next(stc_enum)
      except StopIteration:
          raise RuntimeError("Iterable did not provide stc[0]")
      _, _, verts = _stc_data_event(stc_counted, 1, info["sfreq"])
      return stc_enum, stc_counted, verts
  
imports: import os
  from collections.abc import Iterable
  from pathlib import Path
  import numpy
  from .._fiff.constants import FIFF
  from .._fiff.meas_info import Info
  from .._fiff.pick import pick_channels, pick_channels_forward, pick_info, pick_types
  from .._ola import _Interp2
  from ..bem import fit_sphere_to_headshape, make_sphere_model, read_bem_solution
  from ..chpi import _get_hpi_initial_fit, get_chpi_info, head_pos_to_trans_rot_t, read_head_pos
  from ..cov import Covariance, make_ad_hoc_cov, read_cov
  from ..event import _get_stim_channel
  from ..forward import _compute_forwards, _magnetic_dipole_field_vec, _merge_fwds, _prep_meg_channels, _prepare_for_forward, _stc_src_sel, _to_forward_dict, _transform_orig_meg_coils, convert_forward_solution, restrict_forward_to_stc
  from ..io import BaseRaw, RawArray
  from ..source_estimate import _BaseSourceEstimate
  from ..source_space._source_space import _ensure_src, _set_source_space_vertices, setup_volume_source_space
  from ..surface import _CheckInside
  from ..transforms import _get_trans, transform_surface_to
  from ..utils import _check_preload, _pl, _validate_type, check_random_state, logger, verbose
  from .source import SourceSimulator
label_desc: Use image node_id 2 for calling a global function with example usage: _check_stc_iterable(stc, info) and returns: stc_enum,  stc_counted,  verts