book_blocks-8.x-1.4/book_blocks.services.yml

services:
  cache_context.route.book_block_toc:
    class: Drupal\book\Cache\BookNavigationCacheContext
    arguments: ['@request_stack']
    calls:
      - [setContainer, ['@service_container']]
    tags:
      - { name: cache.context}

  cache_context.route.book_block_navigation:
    class: Drupal\book\Cache\BookNavigationCacheContext
    arguments: ['@request_stack']
    calls:
      - [setContainer, ['@service_container']]
    tags:
      - { name: cache.context}