function setForcedSkins($skins, $multicall = false)
    {
        if (is_array($skins)) {
            foreach ($skins as $i => &$skin) {
                if (!($skin instanceof Structures\ForcedSkin)) {
                    throw new InvalidArgumentException('skins[' . $i . '] = ' . print_r($skin, true));
                }
                $skin = $skin->toArray();
            }
        } elseif ($skins instanceof Structures\ForcedSkin) {
            $skins = array($skins->toArray());
        } else {
            throw new InvalidArgumentException('skins = ' . print_r($skins, true));
        }

        return $this->execute(ucfirst(__FUNCTION__), array($skins), $multicall);
    }