Returns: the selected instruments

def get_values(self):
        """
        Returns: the selected instruments
        """
        elements_selected = {}
        for index in range(self.tree_loaded_model.rowCount()):
            element_name = str(self.tree_loaded_model.item(index).text())
            if element_name in self.elements_old:
                elements_selected.update({element_name: self.elements_old[element_name]})
            elif element_name in self.elements_from_file:
                elements_selected.update({element_name: self.elements_from_file[element_name]})


        return elements_selected