public function setEntity($entity = array())
    {
        // check if only one entry is given
        if (count($entity) <> 1) {
            throw new \InvalidArgumentException('Must be set with one key/value-pair!');
        }

        // fetch key from parameter
        $_tmp = array_keys($entity);
        $key  = array_pop($_tmp);

        // check if the key of the given array exists
        if (array_key_exists($key, $this->entityList)) {
            // check if value exists for key
            if (in_array($entity[$key], $this->entityList[$key])) {
                $this->defaultOptions['entity'] = $entity;
            }
        }

        return $this;
    }