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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _handle_processor_error(self, failure):
 """Handle a failure in the processing of a block of messages This method is called when the processor func fails while processing a block of messages. Since we can't know how best to handle a processor failure, we just :func:`errback` our :func:`start` method's deferred to let our user know about the failure. """

        # Check if we're stopping/stopped and the errback of the processor
        # deferred is just the cancelling we initiated.  If so, we skip
        # notifying via the _start_d deferred, as it will be 'callback'd at the
        # end of stop()
        if not (self._stopping and failure.check(CancelledError)):
            if self._start_d:  # Make sure we're not already stopped
                self._start_d.errback(failure)