///addChild(parent, child)
/**
 * addChild :: TreeNode -> TreeNode -> ()
 * 
 * Adds `child` to the list of children in `parent` and sets the parent of the `child` to `parent`.
 *
 * @param parent the parent TreeNode
 * @param child the child TreeNode
 */

ds_list_add(argument0.children, argument1);
argument1.parent = argument0;