Selects a DropDownItem by means of the contained text-

        Args:
            value (str): Textual content of the DropDownItem that have to be selected.

def select_by_value(self, value):
        """Selects a DropDownItem by means of the contained text-

        Args:
            value (str): Textual content of the DropDownItem that have to be selected.
        """
        self._selected_key = None
        self._selected_item = None
        for k in self.children:
            item = self.children[k]
            if item.get_text() == value:
                item.attributes['selected'] = 'selected'
                self._selected_key = k
                self._selected_item = item
            else:
                if 'selected' in item.attributes:
                    del item.attributes['selected']