code: def _st_power_itc(x, start_f, compute_itc, zero_pad, decim, W):
      """Aux function."""
      n_samp = x.shape[-1]
      n_out = n_samp - zero_pad
      n_out = n_out // decim + bool(n_out % decim)
      psd = np.empty((len(W), n_out))
      itc = np.empty_like(psd) if compute_itc else None
      X = fft(x)
      XX = np.concatenate([X, X], axis=-1)
      for i_f, window in enumerate(W):
          f = start_f + i_f
          ST = ifft(XX[:, f : f + n_samp] * window)
          if zero_pad > 0:
              TFR = ST[:, :-zero_pad:decim]
          else:
              TFR = ST[:, ::decim]
          TFR_abs = np.abs(TFR)
          TFR_abs[TFR_abs == 0] = 1.0
          if compute_itc:
              TFR /= TFR_abs
              itc[i_f] = np.abs(np.mean(TFR, axis=0))
          TFR_abs *= TFR_abs
          psd[i_f] = np.mean(TFR_abs, axis=0)
      return psd, itc
  
file_path: mne-python/mne/time_frequency/_stockwell.py
imports: from copy import deepcopy
  import numpy
  from scipy.fft import fft, fftfreq, ifft
  from .._fiff.pick import _pick_data_channels, pick_info
  from ..parallel import parallel_func
  from ..utils import _validate_type, fill_doc, logger, verbose
  from .tfr import AverageTFR, _get_data
label_desc: Use image node_id 4 for calling a global function with example usage: _st_power_itc(x, start_f, compute_itc, zero_pad, decim, W) and returns: psd,  itc