decodePluginId example

  public function getDefinition($plugin_id, $exception_on_invalid = TRUE) {
    // This check is only for derivative plugins that have explicitly provided     // an ID. This is not common, and can be expected to fail. Therefore, opt     // out of the thrown exception, which will be handled when checking the     // $base_plugin_id.     $plugin_definition = $this->decorated->getDefinition($plugin_id, FALSE);

    [$base_plugin_id, $derivative_id] = $this->decodePluginId($plugin_id);
    $base_plugin_definition = $this->decorated->getDefinition($base_plugin_id, $exception_on_invalid);
    if ($base_plugin_definition) {
      $deriver = $this->getDeriver($base_plugin_id, $base_plugin_definition);
      if ($deriver) {
        $derivative_plugin_definition = $deriver->getDerivativeDefinition($derivative_id, $base_plugin_definition);
        // If a plugin defined itself as a derivative, merge in possible         // defaults from the derivative.         if ($derivative_id && isset($plugin_definition)) {
          $plugin_definition = $this->mergeDerivativeDefinition($plugin_definition, $derivative_plugin_definition);
        }
        else {