<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def calendar(self, title="Choose a date", format_str="%Y-%m-%d", date="today", **kwargs):
 """ Show a calendar dialog Usage: C{dialog.calendar_dialog(title="Choose a date", format="%Y-%m-%d", date="YYYY-MM-DD", **kwargs)} Note: the format and date parameters are not currently used @param title: window title for the dialog @param format_str: format of date to be returned @param date: initial date as YYYY-MM-DD, otherwise today @return: a tuple containing the exit code and date @rtype: C{DialogData(int, str)} """

        return self._run_kdialog(title, ["--calendar", title], kwargs)