Expand is non-deterministic if there are parent-child elements

[alexec]

Consider this:

m0 := map[string]interface{}{
				"a.b": 2,
				"a":   1,
			}
			m1 := Expand(m0)
			assert.Len(t, m0, 2, "original map unchanged")
			assert.Equal(t, map[string]interface{}{
				"a": map[string]interface{}{
					"b": 2,
				},
			}, m1)

What should the resulting map be? I think it is undefined?