<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def iter_items(cls, repo, common_path=None):
 """Find all refs in the repository :param repo: is the Repo :param common_path: Optional keyword argument to the path which is to be shared by all returned Ref objects. Defaults to class specific portion if None assuring that only refs suitable for the actual class are returned. :return: git.SymbolicReference[], each of them is guaranteed to be a symbolic ref which is not detached and pointing to a valid ref List is lexicographically sorted The returned objects represent actual subclasses, such as Head or TagReference"""

        return (r for r in cls._iter_items(repo, common_path) if r.__class__ == SymbolicReference or not r.is_detached)