Check out example codes for "@angular/fire/angularfire2.d.ts:37:49 - error TS2344: Type 'T[K]' does not satisfy the constraint '(...args: any) => any". It will help you in understanding the concepts better.

Code Example 1

{
  //...
  compilerOptions: {
    "skipLibCheck": true,
    //...
  }
}

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