When Atoms are in atom, how does focusAtom get the value in atom?

[ouweiya]

When Atoms are in atom, how does focusAtom get the value in atom?

const oneAtom = atom({
    a: 10,
    b: 20,
});
const twoAtom = atom({
    a: 111,
    b: 222,
});

const toogleAtom = atom(oneAtom);

const selectAtom = focusAtom(toogleAtom, optic=> optic.prop('a'));

[dai-shi]

Something like this, but not sure if types work:

atom((get) => focusAtom(get(toggleAtom), (optic) => optic.prop('a')))