Lists the processors.

        Processors are returned in lexicographical order.

        :param Optional[str] instance: A Yamcs instance name.
        :rtype: ~collections.Iterable[.Processor]

def list_processors(self, instance=None):
        """
        Lists the processors.

        Processors are returned in lexicographical order.

        :param Optional[str] instance: A Yamcs instance name.
        :rtype: ~collections.Iterable[.Processor]
        """
        # Server does not do pagination on listings of this resource.
        # Return an iterator anyway for similarity with other API methods
        url = '/processors'
        if instance:
            url += '/' + instance
        response = self.get_proto(path=url)
        message = rest_pb2.ListProcessorsResponse()
        message.ParseFromString(response.content)
        processors = getattr(message, 'processor')
        return iter([Processor(processor) for processor in processors])