docs: def check_req(req):
      """Checks if a given req is the latest version available."""
      if not isinstance(req, Requirement):
          return None
  
      info = get_package_info(req.name)
      newest_version = _get_newest_version(info)
  
      if _is_pinned(req) and _is_version_range(req):
          return None
  
      current_spec = next(iter(req.specifier)) if req.specifier else None
      current_version = current_spec.version if current_spec else None
      if current_version != newest_version:
          return req.name, current_version, newest_version