public function buildCondition(array $configuration, IMetaModel $metaModel)
    {
        // No children, then return "true".
        if (empty($configuration['children'])) {
            return new NotCondition(new BooleanCondition(false));
        }
        if (1 < $count = count($configuration['children'])) {
            throw new \InvalidArgumentException('NOT conditions may only contain one child, ' . $count . ' given.');
        }

        return new NotCondition($this->factory->createCondition($configuration['children'][0], $metaModel));
    }
public function buildCondition(array $configuration, IMetaModel $metaModel)
    {
        // No children, then return "true".
        if (empty($configuration['children'])) {
            return new NotCondition(new BooleanCondition(false));
        }
        if (1 < $count = count($configuration['children'])) {
            throw new \InvalidArgumentException('NOT conditions may only contain one child, ' . $count . ' given.');
        }

        return new NotCondition($this->factory->createCondition($configuration['children'][0], $metaModel));
    }
{@inheritDoc}

@throws \InvalidArgumentException When there are more than one children.