code: def _get_ext_force(filename, force_ext=None):
      if force_ext:
          return str(force_ext).lower()
      else:
          return get_ext(filename)
  
imports: import os
  import pathlib
  import warnings
  import numpy
  import pyvista
  from pyvista.core import _vtk_core
  from pyvista.core.errors import PyVistaDeprecationWarning
  from .observers import Observer
label_desc: Use image node_id 2 for calling a global function with example usage: _get_ext_force(filename, force_ext) and returns: str, get_ext