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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 buffer(self, item):
 """ Receive an item and write it. """

        key = self.get_key_from_item(item)
        if not self.grouping_info.is_first_file_item(key):
            self.items_group_files.add_item_separator_to_file(key)
        self.grouping_info.ensure_group_info(key)
        self.items_group_files.add_item_to_file(item, key)