function getApplyIdentity(M) {
	return fromAssociative(getApplyAssociative(M))(O.none);
}
`Apply` Identity

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