code: def _find_descendents(self, url):
          
          # Ad-hoc query for URL starting with a prefix
          map_fun = """function(doc) {
                  var url = doc.url + "/";
                  if(doc.type === 'properties' && url.indexOf('%s') === 0) {
                      emit(doc.url, { 'id': doc._id, 'url': doc.url });
                  }
              }""" % (
              url + "/"
          )
          vr = self.db.query(map_fun, include_docs=True)
          for row in vr:
              yield row.doc
          return
docs: Return properties document for url and all children.