getChildren method
Returns a list containing the children of this render object.
This function is useful when you need random-access to the children of this render object. If you're accessing the children in order, consider walking the child list directly.
Implementation
List<ChildType> getChildren() {
  final List<ChildType> result = <ChildType>[];
  visitChildren((child) {
    if (child is! RenderPositionPlaceholder) {
      result.add(child as ChildType);
    }
  });
  return result;
}