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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 begin(self):
 """Start a new transaction."""

        if self.in_transaction:  # we're already in a transaction...
            if self._auto_transaction:
                self._auto_transaction = False
                return
            self.commit()
        self.in_transaction = True
        for collection, store in self.stores.items():
            store.begin()
            indexes = self.indexes[collection]
            for index in indexes.values():
                index.begin()