code: def get_cross_talk(
      resmat,
      src,
      idx,
      mode=None,
      *,
      n_comp=1,
      norm=False,
      return_pca_vars=False,
      vector=False,
      verbose=None,
  ):
      """Get cross-talk (CTFs) function for vertices.
  
      Parameters
      ----------
      resmat : array, shape (n_dipoles, n_dipoles)
          Forward Operator.
      src : instance of SourceSpaces | instance of InverseOperator | instance of Forward
          Source space used to compute resolution matrix.
          Must be an InverseOperator if ``vector=True`` and a surface
          source space is used.
      %(idx_pctf)s
      %(mode_pctf)s
      %(n_comp_pctf_n)s
      %(norm_pctf)s
      %(return_pca_vars_pctf)s
      %(vector_pctf)s
      %(verbose)s
  
      Returns
      -------
      %(stcs_pctf)s
      %(pca_vars_pctf)s
      """  # noqa: E501
      return _get_psf_ctf(
          resmat,
          src,
          idx,
          func="ctf",
          mode=mode,
          n_comp=n_comp,
          norm=norm,
          return_pca_vars=return_pca_vars,
          vector=vector,
      )
  
imports: from copy import deepcopy
  import numpy
  from mne.minimum_norm.inverse import InverseOperator
  from .._fiff.constants import FIFF
  from .._fiff.pick import pick_channels_forward
  from ..evoked import EvokedArray
  from ..forward.forward import Forward, convert_forward_solution
  from ..label import Label
  from ..source_estimate import _get_src_type, _make_stc, _prepare_label_extraction
  from ..source_space._source_space import SourceSpaces, _get_vertno
  from ..utils import _validate_type, logger, verbose
  from .inverse import apply_inverse
label_desc: Use image node_id 8 for calling a global function with example usage: get_cross_talk(resmat, src, idx, mode) and returns: _get_psf_ctf