I recommend doing it the other way around with short condition first. Use return to avoid else and the whole thing becomes much easier to read. Basically it avoids having a large amount of code indented inside an if. I.e.

    if num_results:
        self.tag_ref = tag_result['QueryResult']['Results'][0]['_ref']
        return

    create_args = {
        'Tag': {
            'Name': self.config['alm_issue_label'],
            'Workspace': self.workspace_ref,
        }
+            }