code: def _sphere_field(rrs, coils, sphere):
      """Compute field for spherical model using Jukka Sarvas' field computation.
  
      Jukka Sarvas, "Basic mathematical and electromagnetic concepts of the
      biomagnetic inverse problem", Phys. Med. Biol. 1987, Vol. 32, 1, 11-22.
  
      The formulas have been manipulated for efficient computation
      by Matti Hämäläinen, February 1990
      """
      rmags, cosmags, ws, bins = _triage_coils(coils)
      return _do_sphere_field(
          rrs, rmags, cosmags, ws, bins, sphere["r0"]
      )
  
imports: from copy import deepcopy
  import numpy
  from .._fiff.constants import FIFF
  from ..bem import _import_openmeeg, _make_openmeeg_geometry
  from ..fixes import bincount, jit
  from ..parallel import parallel_func
  from ..surface import _jit_cross, _project_onto_surface
  from ..transforms import apply_trans, invert_transform
  from ..utils import _check_option, _pl, fill_doc, logger, verbose, warn
label_desc: Use image node_id 15 for calling a global function with example usage: _sphere_field(rrs, coils, sphere) and returns: _do_sphere_field