Function isFormString

isFormString(string_: string): string_ is `L${number}-F${number}`
Tests if a string is a FormString. Can also be used as a type guard.
Parameters
- string_: string
  The string to test.
Returns string_ is `L${number}-F${number}`
True if the string is a FormString.
Example
```
const id = 'L123-F4';
   if (!isFormString(id)) {
       throw new Error('Not a FormString');
   }
   WikibaseFormSnak.fromData('P5830', id);
```
- Defined in src/utils/guards/strings.ts:116