@abstractmethod<EOL><INDENT>def shutdown(self):<DEDENT>
raise NotImplementedError('<STR_LIT>')<EOL>
Do an orderly shutdown of this stage.

        If the stage spawns a child process, kill it, and do any other
        required cleanup.  :meth:`streamcorpus_pipeline.Pipeline._cleanup`
        will call this method on every batch transform stage, regardless
        of whether this is the currently running stage or not.