code: def install(self, backend='money.exchange.SimpleBackend'):
          
          # RADAR: Python2
          if isinstance(backend, money.six.string_types):
              path, name = backend.rsplit('.', 1)
              module = importlib.import_module(path)
              backend = getattr(module, name)()
          elif isinstance(backend, type):
              backend = backend()
          if not isinstance(backend, BackendBase):
              raise TypeError("backend '{}' is not a subclass of "
                              "money.xrates.BackendBase".format(backend))
          self._backend = backend
docs: Install an exchange rates backend using a python path string