<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def select_by_value(self, value):
 """Selects an item by the text content of the child. Args: value (str):
 Text content of the item that have to be selected. """

        self._selected_key = None
        self._selected_item = None
        for k in self.children:
            item = self.children[k]
            item.attributes['selected'] = False
            if value == item.get_value():
                self._selected_key = k
                self._selected_item = item
                self._selected_item.attributes['selected'] = True