One-off code generation using append.
        
        If keyword args are provided, initialized using 
        :meth:`with_id_processor`.

def append_once(cls, code, **kwargs):
        """One-off code generation using append.
        
        If keyword args are provided, initialized using 
        :meth:`with_id_processor`.
        """
        if kwargs:
            g = cls.with_id_processor()
            g._append_context(kwargs)
        else:
            g = cls()
        g.append(code)
        return g.code