Problem with adjusting value during runtime in my OOT block

[Nikoloz Glonti]

Dear Gnuradio community,

I wrote my block in OOT module. It has function set_constant0(int 
constant0) which should change value on the go.
I also added callback to grc yaml file. But when I run my flowgraph, I'm 
having this error "AttributeError: 'SiNK.SiNK_python.adding_ff' object 
has no attribute 'set_constant0'" .

How can i fix it?

Niko