def addValue(self, type_uri, value):
        """Add a single value for the given attribute type to the
        message. If there are already values specified for this type,
        this value will be sent in addition to the values already
        specified.

        @param type_uri: The URI for the attribute

        @param value: The value to add to the response to the relying
            party for this attribute
        @type value: unicode

        @returns: None
        """
        try:
            values = self.data[type_uri]
        except KeyError:
            values = self.data[type_uri] = []

        values.append(value)
Add a single value for the given attribute type to the
        message. If there are already values specified for this type,
        this value will be sent in addition to the values already
        specified.

        @param type_uri: The URI for the attribute

        @param value: The value to add to the response to the relying
            party for this attribute
        @type value: unicode

        @returns: None