code: def _check_zooms(mri_from, zooms, zooms_src_to):
      # use voxel size of mri_from
      if isinstance(zooms, str) and zooms == "auto":
          zooms = zooms_src_to if zooms_src_to is not None else 5.0
      if zooms is None:
          zooms = mri_from.header.get_zooms()[:3]
      zooms = np.atleast_1d(zooms).astype(float)
      if zooms.shape == (1,):
          zooms = np.repeat(zooms, 3)
      if zooms.shape != (3,):
          raise ValueError(
              "zooms must be None, a singleton, or have shape (3,),"
              " got shape %s" % (zooms.shape,)
          )
      zooms = tuple(zooms)
      return zooms
  
imports: import copy
  import os.path
  import warnings
  import numpy
  from scipy import sparse
  from .fixes import _get_img_fdata
  from .morph_map import read_morph_map
  from .parallel import parallel_func
  from .source_estimate import _BaseSourceEstimate, _BaseSurfaceSourceEstimate, _BaseVolSourceEstimate, _get_ico_tris
  from .source_space._source_space import SourceSpaces, _ensure_src, _grid_interp
  from .surface import _compute_nearest, mesh_edges, read_surface
  from .utils import BunchConst, ProgressBar, _check_fname, _check_option, _custom_lru_cache, _ensure_int, _import_h5io_funcs, _import_nibabel, _validate_type, check_version, fill_doc, get_subjects_dir, logger, use_log_level, verbose, warn
  from .utils import warn
label_desc: Use image node_id 4 for calling a global function with example usage: _check_zooms(mri_from, zooms, zooms_src_to) and returns: zooms