Processing the pipeline.

def run(self, definition):
        """Processing the pipeline."""
        self.logger.info("Running with Python %s", sys.version.replace("\n", ""))
        self.logger.info("Running on platform %s", platform.platform())
        self.logger.info("Current cpu count is %d", multiprocessing.cpu_count())
        self.logger.info("Processing pipeline definition '%s'", definition)

        document = self.validate_document(definition)
        if self.options.validate_only:
            self.logger.info("Stopping after validation as requested!")
            return []

        self.provide_temporary_scripts_path()

        versions = VersionsCheck().process(document)
        VersionsReport().process(versions)

        collector = Application.create_and_run_collector(document, self.options)
        matrix = find_matrix(document)
        output = []
        if len(matrix) == 0:
            model = {} if 'model' not in document else document['model']
            pipeline = Pipeline(model=model, options=self.options)
            pipeline.hooks = Hooks(document)
            result = pipeline.process(document['pipeline'])
        else:
            result = self.run_matrix(matrix, document)

        output = result['output']
        self.shutdown(collector, success=result['success'])
        return output