def METHOD_NAME(self):
    if len(self._possible_items) == 0:
        QMessageBox.information(
            self, "No items", "No items available for selection!"
        )
    else:
        item, ok = QInputDialog.getItem(
            self,
            "Select a case",
            "Select a case to add to the case list:",
            self._possible_items,
        )
        if ok:
            item = str(item).strip()
            text = str(self._list_edit_line.text()).rstrip()
            if len(text) == 0:
                text = item + ", "
            elif text.endswith(","):
                text += " " + item
            else:
                text += ", " + item
            self._list_edit_line.setText(text)