JsonbValue to Jsonb conversion

Hi all,

I'm faced with some troubles about the jsonb implementation, and I hope
I'll get little advice =)
If I understand correctly, an abstract function for jsonb modification
should have the following stages:

Jsonb -> JsonbValue -> Modification -> JsonbValue -> Jsonb

One can convert the *JsonbValue* to the *Jsonb* only by *JsonbValueToJsonb*
function. So, my question is can be *JsonbValue*, that contains few
*jbvBinary* elements, converted to *Jsonb* by this function? It will be
very useful, if you want modify only small part of your JsonbValue (e.g.
replace value of some key). But when I'm trying to do this, an exception
"unknown type of jsonb container" appears. Maybe I missed something? Or is
there another approach to do this conversion?