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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(self, force_first=False, force_last=False, force_column=None, force_widget=None):
 """ Call this to give this Layout the input focus. :param force_first: Optional parameter to force focus to first widget. :param force_last: Optional parameter to force focus to last widget. :param force_column: Optional parameter to mandate the new column index. :param force_widget: Optional parameter to mandate the new widget index. The force_column and force_widget parameters must both be set together or they will otherwise be ignored. :raises IndexError: if a force option specifies a bad column or widget, or if the whole Layout is readonly. """

        self._has_focus = True
        if force_widget is not None and force_column is not None:
            self._live_col = force_column
            self._live_widget = force_widget
        elif force_first:
            self._live_col = 0
            self._live_widget = -1
            self._find_next_widget(1)
        elif force_last:
            self._live_col = len(self._columns) - 1
            self._live_widget = len(self._columns[self._live_col])
            self._find_next_widget(-1)
        self._columns[self._live_col][self._live_widget].focus()