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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 serialize_payload(self):
 """ Serializes the marker output data into a payload buffer. :return: The serialized payload. :rtype: bytes """

        with io.BytesIO() as stream:
            stream.write(self.OPEN_ASSETS_TAG)

            bitcoin.core.VarIntSerializer.stream_serialize(len(self.asset_quantities), stream)
            for asset_quantity in self.asset_quantities:
                stream.write(self.leb128_encode(asset_quantity))

            bitcoin.core.VarIntSerializer.stream_serialize(len(self.metadata), stream)

            stream.write(self.metadata)

            return stream.getvalue()