loopback-datasource-juggler datasource definition for setup method is missing

Steps to reproduce

At https://github.com/strongloop/loopback-datasource-juggler/blob/master/types/datasource.d.ts,
there is no definition for method setup, which is defined at:
https://github.com/strongloop/loopback-datasource-juggler/blob/06428247ad1cc48bce82d135f795fb3eaae28b33/lib/datasource.js#L382

1. I create custom datasource class MyDataSource which extends juggler.Datasource.
2. I create method setup inside class MyDataSource .
3. I can not use: super.setup() inside method setup.

Current Behavior

When I want to use super.setup(), there will be ts error: Property 'setup' does not exists on type 'Datasource'.

Expected Behavior

No ts error when I want to use super.setup() inside setup method on my custom datasource class.

Additional information

Setup method definition:

  /**
   * Setup datasource
   * @param dsName The name of the datasource.
   * @param settings The datasource settings
   */
  setup(dsName: string, settings: Options): void;
  setup(settings: Options): void;