code: def get_active_chpi(raw, *, on_missing="raise", verbose=None):
      """Determine how many HPI coils were active for a time point.
  
      Parameters
      ----------
      raw : instance of Raw
          Raw data with cHPI information.
      %(on_missing_chpi)s
      %(verbose)s
  
      Returns
      -------
      n_active : array, shape (n_times)
          The number of active cHPIs for every timepoint in raw.
  
      Notes
      -----
      .. versionadded:: 1.2
      """
      # get meg system
      system, _ = _get_meg_system(raw.info)
  
      # check whether we have a neuromag system
      if system not in ["122m", "306m"]:
          raise NotImplementedError(
              "Identifying active HPI channels is not implemented for other systems than "
              "neuromag."
          )
      # extract hpi info
      chpi_info = get_chpi_info(raw.info, on_missing=on_missing)
      if (len(chpi_info[2]) == 0) or (chpi_info[1] is None):
          return np.zeros_like(raw.times)
  
      # extract hpi time series and infer which one was on
      chpi_ts = raw[chpi_info[1]][0].astype(int)
      chpi_active = (chpi_ts & chpi_info[2][:, np.newaxis]).astype(bool)
      return chpi_active.sum(axis=0)
  
imports: import copy
  import itertools
  from functools import partial
  import numpy
  from scipy.linalg import orth
  from scipy.optimize import fmin_cobyla
  from scipy.spatial.distance import cdist
  from ._fiff.constants import FIFF
  from ._fiff.meas_info import Info, _simplify_info
  from ._fiff.pick import _picks_to_idx, pick_channels, pick_channels_regexp, pick_info, pick_types
  from ._fiff.proj import Projection, setup_proj
  from .channels.channels import _get_meg_system
  from .cov import compute_whitener, make_ad_hoc_cov
  from .dipole import _make_guesses
  from .event import find_events
  from .fixes import jit
  from .forward import _concatenate_coils, _create_meg_coils, _magnetic_dipole_field_vec
  from .io import BaseRaw
  from .io.ctf.trans import _make_ctf_coord_trans_set
  from .io.kit.constants import KIT
  from .io.kit.kit import RawKIT
  from .preprocessing.maxwell import _get_mf_picks_fix_mags, _prep_mf_coils, _regularize_out, _sss_basis
  from .transforms import _angle_between_quats, _fit_matched_points, _quat_to_affine, als_ras_trans, apply_trans, invert_transform, quat_to_rot, rot_to_quat
  from .utils import ProgressBar, _check_fname, _check_option, _on_missing, _pl, _validate_type, _verbose_safe_false, logger, use_log_level, verbose, warn
label_desc: Use image node_id 34 for calling a global function with example usage: get_active_chpi(raw) and returns: chpi_active, np