code: def _get_create_subjects_dir(subjects_dir):
      subjects_dir = get_subjects_dir(subjects_dir, raise_error=False)
      if subjects_dir is None:
          subjects_dir = _get_path(
              None, "MNE_DATA", "montage coregistration"
          )
          subjects_dir = op.join(subjects_dir, "MNE-fsaverage-data")
          os.makedirs(subjects_dir, exist_ok=True)
      else:
          subjects_dir = str(subjects_dir)
      return subjects_dir
  
imports: import os
  import os.path
  from ...utils import get_subjects_dir, set_config, verbose
  from ..utils import _get_path, _manifest_check_download
label_desc: Use image node_id 2 for calling a global function with example usage: _get_create_subjects_dir(subjects_dir) and returns: subjects_dir