public function replace($name, $value) {
        if (!isset($this->unresolvedDeps[$name])) {
            throw new Exception("Dependency does not exist: $name!");
        }
        if (isset($this->resolvedDeps[$name])) {
            throw new Exception("Could replace resolved Dependency: $name!");
        }
        $this->unresolvedDeps[$name] = &$value;
    }