function isElement(x) {
    if (!x || typeof x !== 'object') { return false; }
    if (typeof HTMLElement !== 'undefined' && x instanceof HTMLElement) {
        return true;
    }
    return typeof x.nodeName === 'string' && typeof x.getAttribute === 'function';
}
Determine if message is already finished.

@param {object} msg
@return {boolean}
@public