def invoice_recipient(self):
<EOL>slf = AttendeeProfileBase.objects.get_subclass(id=self.id)<EOL>if type(slf).invoice_recipient != type(self).invoice_recipient:<EOL><INDENT>return type(slf).invoice_recipient(slf)<EOL><DEDENT>return slf.attendee.user.username<EOL>
Returns:
    A representation of this attendee profile for the purpose
    of rendering to an invoice. This should include any information
    that you'd usually include on an invoice. Override in subclasses.