code: def import_from_json(self, data):
          
          self.version = data.get("ver", None)
  
          self.items.clear()
          self.groups.clear()
          for jid, data in data.get("items", {}).items():
              jid = structs.JID.fromstr(jid)
              item = Item(jid)
              item.update_from_json(data)
              self.items[jid] = item
              for group in item.groups:
                  self.groups.setdefault(group, set()).add(item)
docs: Replace the current roster with the :meth:`export_as_json`-compatible
          dictionary in `data`.
  
          No events are fired during this activity. After this method completes,
          the whole roster contents are exchanged with the contents from `data`.
  
          Also, no data is transferred to the server; this method is intended to
          be used for roster versioning. See below (in the docs of
          :class:`Service`).