code: def _parse_ext(ext):
      if ext is None:
          return None
  
      if not ext.startswith("."):
          ext = "." + ext
  
      return ext.lower()
  
imports: import logging
  import os
  import eta.core.image
  import eta.core.utils
  import fiftyone.core.storage
  import fiftyone.core.utils
  import fiftyone.core.validation
label_desc: Use image node_id 13 for calling a global function with example usage: _parse_ext(ext) and returns: ext, None