code: def to_vobjects(self, filename, uids=None):
          
          self._update()
  
          if not uids:
              uids = self.get_uids(filename)
  
          items = []
  
          for uid in uids:
              entry = self._book[uid.split('@')[0]]
              # TODO add getmtime of photo
              etag = sha1(str(dict(entry)).encode('utf-8'))
              items.append((uid, self._to_vcard(entry), '"%s"' % etag.hexdigest()))
          return items
docs: Return vCards and etags of all Abook entries in uids
          filename  -- unused, for API compatibility only
          uids -- the UIDs of the Abook entries (all if None)