ui.Interface.getChildCount
Get the number of children in a parent container.
Syntax
ui.Interface.getChildCount()
  RETURNS INTEGER
Usage
Important: The Window Container Interface is a desktop application
feature (for GDC), and is not supported on other front-ends (web and mobile).
The ui.Interface.getChildCount() class method returns the number of child
        programs attached to the current parent WCI program.
WCI child programs are attached to a given container by using the ui.Interface.setContainer() method. Container and child program
        identifiers/names are defined by the ui.Interface.setName() method.