code: def get(self, key, env=None):
          
          if env is None:
              env = self.environment
          try:
              ret = self._settings[env][key]
          except KeyError:
              ret = None
          if ret is None:
              # See if it's set in the environment
              if key == "identity_class":
                  # This is defined via the identity_type
                  env_var = self.env_dct.get("identity_type")
                  ityp = os.environ.get(env_var)
                  if ityp:
                      return _import_identity(ityp)
              else:
                  env_var = self.env_dct.get(key)
              if env_var is not None:
                  ret = os.environ.get(env_var)
          return ret
docs: Returns the config setting for the specified environment. If no
          environment is specified, the value for the current environment is
          returned. If an unknown key or environment is passed, None is returned.