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