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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def focus_notebook_page_of_controller(self, controller):
 """Puts the focus on the given child controller The method implements focus request of the notebooks in left side-bar of the main window. Thereby it is the master-function of focus pattern of the notebooks in left side-bar. Actual pattern is: * Execution-History is put to focus any time requested (request occur at the moment when the state-machine is started and stopped. * Modification-History one time focused while and one time after execution if requested. :param controller The controller which request to be focused. """

        # TODO think about to may substitute Controller- by View-objects it is may the better design
        if controller not in self.get_child_controllers():
            return
        # logger.info("focus controller {0}".format(controller))
        if not self.modification_history_was_focused and isinstance(controller, ModificationHistoryTreeController) and \
                self.view is not None:
            self.view.bring_tab_to_the_top('history')
            self.modification_history_was_focused = True

        if self.view is not None and isinstance(controller, ExecutionHistoryTreeController):
            self.view.bring_tab_to_the_top('execution_history')
            self.modification_history_was_focused = False