code: def _setup_hpi_glm(hpi_freqs, line_freqs, sfreq, window_nsamp):
      """Initialize a general linear model for HPI amplitude estimation."""
      slope = np.linspace(-0.5, 0.5, window_nsamp)[:, np.newaxis]
      radians_per_sec = (
          2 * np.pi * np.arange(window_nsamp, dtype=float) / sfreq
      )
      f_t = hpi_freqs[np.newaxis, :] * radians_per_sec[:, np.newaxis]
      l_t = line_freqs[np.newaxis, :] * radians_per_sec[:, np.newaxis]
      model = [
          np.sin(f_t),
          np.cos(f_t),  # hpi freqs
          np.sin(l_t),
          np.cos(l_t),  # line freqs
          slope,
          np.ones_like(slope),
      ]  # drift, DC
      return np.hstack(model)
  
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 16 for calling a global function with example usage: _setup_hpi_glm(hpi_freqs, line_freqs, sfreq, window_nsamp) and returns: np