plugin_type_example.services.yml

# This declares the plugin manager to the service container. For background
# information on the service container, see https://www.drupal.org/node/2133171.
# Changes here require that the cache be cleared in order to have Drupal notice
# them.
services:
  # The machine name of the service. This is the string that must be passed to
  # Drupal::service() to get the instantiated plugin manager.
  plugin.manager.sandwich:
    # This tells the service container the name of our plugin manager class.
    class: Drupal\plugin_type_example\SandwichPluginManager
    parent: default_plugin_manager