id: d6_book
label: Books
migration_tags:
  - Drupal 6
  - Content
source:
  plugin: d6_book
process:
  nid: nid
  'book/bid': bid
  'book/weight': weight
  'book/pid':
    -
      plugin: skip_on_empty
      method: process
      source: plid
    -
      plugin: migration_lookup
      migration: d6_book
destination:
  plugin: book
migration_dependencies:
  required:
    - d6_node