code: def _read_isotrak_elp_points(fname):
      """Read Polhemus Isotrak digitizer data from a ``.elp`` file.
  
      Parameters
      ----------
      fname : path-like
          The filepath of .elp Polhemus Isotrak file.
  
      Returns
      -------
      out : dict of arrays
          The dictionary containing locations for 'nasion', 'lpa', 'rpa'
          and 'points'.
      """
      value_pattern = r"\-?\d+\.?\d*e?\-?\d*"
      coord_pattern = rf"({value_pattern})\s+({value_pattern})\s+({value_pattern})\s*$"
  
      with open(fname) as fid:
          file_str = fid.read()
  
      points_str = [
          m.groups()
          for m in re.finditer(coord_pattern, file_str, re.MULTILINE)
      ]
      points = np.array(points_str, dtype=float)
  
      return {
          "nasion": points[0],
          "lpa": points[1],
          "rpa": points[2],
          "points": points[3:],
      }
  
imports: import os.path
  import re
  from collections import OrderedDict
  from copy import deepcopy
  from dataclasses import dataclass
  import numpy
  from .._fiff._digitization import _coord_frame_const, _count_points_by_type, _ensure_fiducials_head, _format_dig_points, _get_data_as_dict_from_dig, _get_dig_eeg, _get_fid_coords, _make_dig_points, _read_dig_fif, write_dig
  from .._fiff.constants import CHANNEL_LOC_ALIASES, FIFF
  from .._fiff.meas_info import create_info
  from .._fiff.open import fiff_open
  from .._fiff.pick import _picks_to_idx, channel_type, pick_types
  from .._freesurfer import get_mni_fiducials
  from ..defaults import HEAD_SIZE_DEFAULT
  from ..transforms import Transform, _ensure_trans, _fit_matched_points, _frame_to_str, _quat_to_affine, _sph_to_cart, _topo_to_sph, _verbose_frames, apply_trans, get_ras_to_neuromag_trans
  from ..utils import _check_fname, _check_option, _on_missing, _pl, _validate_type, copy_function_doc_to_method_doc, fill_doc, verbose, warn
  from ..utils.docs import docdict
  from ..viz import plot_montage
  from ._dig_montage_utils import _parse_brainvision_dig_montage, _read_dig_montage_egi
label_desc: Use image node_id 15 for calling a global function with example usage: _read_isotrak_elp_points(fname) and returns: dict