Complex types serialization

[readysloth]

Hi all

I defined my own type, lets name it A, and created table : 
    
    
    var dictionary = new_table[A, Hash_set[A]]()
    
    
    Run

Now i want serialize this data, but failed to do this, currently. I tried json 
module, but, as spec says, Json cant represent complex types as keys in 
dictionaries. So I felt back on marshal module, which, actually, creates json 
from my table, but when I try compile code with deserialization: 
    
    
    var unmarshalled = read_file("marshalled.json").to[typeof(dictionary)]
    
    
    Run

it throws 
    
    
    /lib/marshal.nim(317,10) Error: cannot instantiate : 'T'
    
    
    Run

What can i do, to serialize this structure?

My nim compiler version is 1.0.6