Define instance member properties in class 'HttpClient ' as instance member methods

Instead of rewriting the templates, I want to be able to extend the underlying HttpClient class, e.g.:

```
class ApiWithErrorHandling extends Api {

async request(params: FullRequestParams): Promise> {
try {
return super.request(params);
} catch (e) {
// do error handling (e.g. logout)
throw e;
}
}

}
```

which results in the following error:

`Class 'Api ' defines instance member property 'request', but extended class 'ApiWithErrorHandling' defines it as instance member function.`

Is there any reason, why the HttpClient class is designed that way?