code: def collection_names(self, _deadline=None):
          
          def ok(results):
              names = [r["name"] for r in results]
              names = [n[len(str(self)) + 1:] for n in names
                       if n.startswith(str(self) + ".")]
              names = [n for n in names if "$" not in n]
              return names
          return self["system.namespaces"].find(_deadline=_deadline).addCallback(ok)
docs: collection_names()