code: def _compute_depth(
      dip, fname_bem, fname_trans, subject, subjects_dir
  ):
      """Compute dipole depth."""
      trans = _get_trans(fname_trans)[0]
      bem = read_bem_solution(fname_bem)
      surf = _bem_find_surface(bem, "inner_skull")
      points = surf["rr"]
      points = apply_trans(trans["trans"], points)
      depth = _compute_nearest(points, dip.pos, return_dists=True)[1][0]
      return np.ravel(depth)
  
imports: import os
  import matplotlib.pyplot
  import numpy
  import pytest
  from numpy.testing import assert_allclose, assert_array_equal, assert_array_less
  from mne import Dipole, DipoleFixed, Epochs, Evoked, EvokedArray, SourceEstimate, convert_forward_solution, fit_dipole, head_to_mni, make_ad_hoc_cov, make_fixed_length_events, make_forward_solution, make_sphere_model, pick_info, pick_types, read_cov, read_dipole, read_evokeds, read_forward_solution, read_source_spaces, transform_surface_to, write_evokeds
  from mne._fiff.constants import FIFF
  from mne.bem import _bem_find_surface, read_bem_solution
  from mne.datasets import testing
  from mne.dipole import _BDIP_ERROR_KEYS, get_phantom_dipoles
  from mne.io import read_raw_ctf, read_raw_fif
  from mne.proj import make_eeg_average_ref_proj
  from mne.simulation import simulate_evoked
  from mne.surface import _compute_nearest
  from mne.transforms import _get_trans, apply_trans
  from mne.utils import _record_warnings, requires_mne, run_subprocess
label_desc: Use image node_id 9 for calling a global function with example usage: _compute_depth(dip, fname_bem, fname_trans, subject, subjects_dir) and returns: np