i dont know the way to get the value of observable 2 inside the last map, here is an example

```
return observable1.pipe(
map((value1: value1) => {
 return observable2;
 }),
mergeMap((value2: value2) => {
 return observable3;
 }),
 map((value3: value3) => {
 // how can i get value 2 inside here?
 }),
 mapTo(null) 
);

```