build an assignment between a function call ASTnode and one of the outputs of the node.
at runtime, when the AST is evaluated this means, call the function, and assign the result to the identifier which is represented by the output port of the node.
the function you call should be defined in some other assembly (not the one containing your nodeModel) - it also cannot be a lamda.
I can try to clarify a bit more - inside the buildAST function you should only deal with AST nodes - the function is not guaranteed to execute every time the node does - it’s like a compile step, sometimes you don’t need to recompile the node to execute it.
The suggestion above should let you return the result of that function call to the output port of your node, but from your question, I’m not sure thats what you need.