code: def is_url_or_existing_file(url_or_filename: Union[str, Path, None]) -> bool:
      
      if url_or_filename is None:
          return False
      url_or_filename = os.path.expanduser(str(url_or_filename))
      parsed = urlparse(url_or_filename)
      return parsed.scheme in ('http', 'https', 's3') or os.path.exists(url_or_filename)
docs: Given something that might be a URL (or might be a local path),
      determine check if it's url or an existing file path.