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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 convert(self, key, value):
 """Get the serialized value for a given key."""

        if key not in self._dtypes:
            self.read_types()
            if key not in self._dtypes:
                name = utils.name(value)
                serializer = utils.serializer(name)
                deserializer = utils.deserializer(name)
                self._dtypes[key] = (name, serializer, deserializer)
                with self.db:
                    self.db.execute("replace into value_types (key, value_type) values (?, ?)", (key, name))
        return self._dtypes[key][1](value)