NS_IMETHOD SetElementAt(PRUint32 index, nsISupports* value) { PRBool ok = ReplaceElementAt(value, index);
NS_IMETHOD SetElementAt(PRUint32 aIndex, nsISupports* value) { PRBool ok = ReplaceElementAt(value, aIndex);
  NS_IMETHOD SetElementAt(PRUint32 index, nsISupports* value) {    PRBool ok = ReplaceElementAt(value, index);    return ok ? NS_OK : NS_ERROR_FAILURE;  }