<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def links(cls, page):
 """return all links on a page, including potentially rel= links."""

    for match in cls.HREF_RE.finditer(page):
      yield cls.href_match_to_url(match)