How to use the @apollo/client/core.Observable function in @apollo/client

request(operation: Operation, _next: NextLink): Observable {
    return new Observable((observer) => {
      var channelId = Math.round(Date.now() + Math.random() * 100000).toString(16)
      var actionName = this.actionName
      var connectionParams = (typeof this.connectionParams === "function") ?
        this.connectionParams(operation) : this.connectionParams
      var channel = this.cable.subscriptions.create(Object.assign({},{
        channel: this.channelName,
        channelId: channelId
      }, connectionParams), {
        connected: function() {
          channel.perform(
            actionName,
            {
              query: operation.query ? print(operation.query) : null,
              variables: operation.variables,
              // This is added for persisted operation support:
              operationId: (operation as {operationId?: string}).operationId,