XState: Guarded Transitions from `done.invoke.<service>`

gistfile1.txt

...
validating: {
  invoke: {
    src: 'validateMobileNumber',
    onDone: [
      {
        target: 'valid',
        actions: assign({mobileNumberError: ''}),
        cond: (_ctx, event) => {
          const validationResponse = event.data;
          if (validationResponse.result) {
            return true;
          } else {
            return false;
          }
        }
      },
      // If the condition is false, validation failed, so go to invalid
      {
        target: 'invalid',
        actions: assign((_ctx, event) => ({ mobileNumberError: event.data.validationMessage }))
      }
    ],
    onError: { ... }