code: def set(self, key, value):
          
          cmd = [
              "heroku",
              "config:set",
              "{}={}".format(key, quote(str(value))),
              "--app",
              self.name,
          ]
          if self._is_sensitive_key(key):
              self._run_quiet(cmd)
          else:
              self._run(cmd)
docs: Configure an app key/value pair