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

        $this->callback = 'none' === $this->configuration['space'] ? 'removeWhitespaceAroundToken' : 'ensureWhitespaceAroundToken';
    }
public function configure(array $configuration = null)
    {
        parent::configure($configuration);

        $this->callback = 'none' === $this->configuration['space'] ? 'removeWhitespaceAroundToken' : 'ensureWhitespaceAroundToken';
    }
{@inheritdoc}