code: def _fast_fit(this_data, proj, n_freqs, model, inv_model_reord):
      # first or last window
      if this_data.shape[1] != model.shape[0]:
          model = model[: this_data.shape[1]]
          inv_model_reord = _reorder_inv_model(
              np.linalg.pinv(model), n_freqs
          )
      proj_data = proj @ this_data
      X = inv_model_reord @ proj_data.T
  
      sin_fit = np.zeros((n_freqs, X.shape[1]))
      for fi in range(n_freqs):
          # use SVD across all sensors to estimate the sinusoid phase
          u, s, vt = np.linalg.svd(
              X[2 * fi : 2 * fi + 2], full_matrices=False
          )
          # the first component holds the predominant phase direction
          # (so ignore the second, effectively doing s[1] = 0):
          sin_fit[fi] = vt[0] * s[0]
      return sin_fit
  
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 21 for calling a global function with example usage: _fast_fit(this_data, proj, n_freqs, model, inv_model_reord) and returns: sin_fit