code: func (g *Graph) ast() {
  
  	if g == nil {
  		return
  	}
  
  	for _, node := range g.Out {
  		if node.ThisString() == TypeExpression {
  			node._ast()
  		} else {
  			node.ast()
  		}
  	}
  }
docs: // Ast reorganizes the expression graph in the form of an abstract syntax tree.