public function push($value, $key = null)
    {
        if (!is_array($this->value)) {
            throw new EvaluationException('Array operation on non-array context', 1344418485);
        }
        if ($key === null) {
            $this->value[] = $value;
        } else {
            $this->value[$key] = $value;
        }
        return $this;
    }