Y: Making a Voom plugin

To invoke a Voom plugin within example.yaml:

//-examplemethod: !callback { args: [ examplecallbackarg ] }

To declare the Voom plugin, create a file called example.plugin.inc with the method defined inside:

namespace Drupal\Y\VoomPlugin;
class example extends \Drupal\Y\VoomPlugin {
  function examplemethod( $examplecallbackarg ) {
  }
}