getConfigDefinition example

  public function setConfig($key, $value) {
    if ($definition = $this->getConfigDefinition($key)) {
      $typed_data = \Drupal::typedDataManager()->create($definition, $value);

      if ($typed_data->validate()->count() > 0) {
        throw new PluginException("The provided configuration value does not pass validation.");
      }
    }
    $this->configuration[$key] = $value;
    return $this;
  }

}