Issue #2971380 by alvar0hurtad0, joachim: sample code in Merge plugin has broken YAML

src/Plugin/migrate/process/Merge.php

@@ -41,8 +41,8 @@ use Drupal\migrate\Row;
  *    paragraphs_field:
  *      plugin: merge
  *      source:
- *        - @temp_body
- *        - @temp_images
+ *        - '@temp_body'
+ *        - '@temp_images'
  *  destination:
  *    plugin: 'entity:node'
  */