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

        $this->functionsFixMap = [];
        foreach ($this->configuration['functions'] as $key) {
            $this->functionsFixMap[$key] = self::$availableFunctions[$key];
        }
    }
public function configure(array $configuration = null)
    {
        parent::configure($configuration);

        $this->functionsFixMap = [];
        foreach ($this->configuration['functions'] as $key) {
            $this->functionsFixMap[$key] = self::$availableFunctions[$key];
        }
    }
{@inheritdoc}