isSet

const a = ""
sb.isSet(a)

-> false

const a = { 
  a: [
    { a: [1, 2, 3] }
  ],
  b: 4
}
​
​
sb.isSet(sb.get(a, 'a.0.a.1'))

-> true

sb.isEmpty(sb.get(a, 'a.0.b.1'))

-> false

sb.isSet(sb.get(a, 'a.0.b.1'))

-> false