public function configure(array $configuration = null)
    {
        parent::configure($configuration);

        $this->classElementTypes = []; // reset previous configuration
        foreach ($this->configuration['elements'] as $element) {
            $this->classElementTypes[$element] = true;
        }
    }
public function configure(array $configuration = null)
    {
        parent::configure($configuration);

        $this->classElementTypes = []; // reset previous configuration
        foreach ($this->configuration['elements'] as $element) {
            $this->classElementTypes[$element] = true;
        }
    }
{@inheritdoc}