test1: ---
assert(a!!)
       |
       false
---
test2: ---
assert(a!!.length == 5)
       |   |      |
       |   |      false
       |   4
       test
---
test3: ---
assert(a.value!!.length == 5)
       | |       |      |
       | |       |      false
       | |       4
       | Test
       Holder
---
test4: ---
assert(a["a"]!! == 43)
       ||       |
       ||       false
       |42
       {a=42}
---
test5: ---
assert(a!!.next!!.next != null)
       |   |      |    |
       |   |      |    false
       |   |      null
       |   Node
       Node
---
