Assign a serializer for the type.

        :param _type: (Type), the target type of the serializer
        :param serializer: (Serializer), Custom Serializer constructor function

def set_custom_serializer(self, _type, serializer):
        """
        Assign a serializer for the type.

        :param _type: (Type), the target type of the serializer
        :param serializer: (Serializer), Custom Serializer constructor function
        """
        validate_type(_type)
        validate_serializer(serializer, StreamSerializer)
        self._custom_serializers[_type] = serializer