function getLastIdentity() {
	return fromAssociative(getLastAssociative())(O.none);
}
`Identity` returning the left-most non-`None` value

| x       | y       | combine(y)(x) |
| ------- | ------- | ------------- |
| none    | none    | none          |
| some(a) | none    | some(a)       |
| none    | some(a) | some(a)       |
| some(a) | some(b) | some(a)       |