def placeChildren(self):
raise(AttributeError("<STR_LIT>"))<EOL>
Create child object(s) main_widget instances.  Place them to the layout.

        Along these lines:

        ::

            for child in self.children:
              child.makeWidget(self.grid_widget) # re-create widgets in the child objects .. their parent is the grid
              child.main_widget.setParent(self.grid_widget) # set widget parent/child relation