TS Error: The property "isReady" / "token" is not available for the "myClient" type.

import { Client } from "@discordjs/core";

export class myClient extends Client {
  async myFunction(...) {
    if (!(this.isReady() || this.token))
    // The property "isReady" / "token" is not available for the "myClient" type.
  }
}

import { Client } from "@discordjs/core";

export class myClient extends Client {
  async myFunction(...) {
    if (!(this.isReady() || this.token))
    // The property "isReady" / "token" is not available for the "myClient" type.
  }
}