I am trying to flatten an array and am getting an error - - error TS2769: No overload matches this call.

I did this in stackblitz and it worked fine.

The spread operator is getting the error: ...this.selectedInstitutions

```
  selectedInstitutions = [
    [{ displayValue: 'ABC', id: 781 }],
    [{ displayValue: 'DEF', id: 782 }],
  ];

  ngOnInit() {
    this.selectedInstitutions = [].concat(...this.selectedInstitutions);
  }

```

The error message is:

[![enter image description here](https://i.stack.imgur.com/6MTNw.png)](https://i.stack.imgur.com/6MTNw.png)