code: def _cached_css_compile(pattern, namespaces, custom, flags):
      
  
      custom_selectors = process_custom(custom)
      return cm.SoupSieve(
          pattern,
          CSSParser(pattern, custom=custom_selectors, flags=flags).process_selectors(),
          namespaces,
          custom,
          flags
      )
docs: Cached CSS compile.