final static boolean isDoubleEscaped(String messagePattern, int delimeterStartIndex) {
        if (delimeterStartIndex >= 2 && messagePattern.charAt(delimeterStartIndex - 2) == ESCAPE_CHAR) {
            return true;
        } else {
            return false;
        }
    }
Assumes that argArray only contains arguments with no throwable as last element.

@param messagePattern
@param argArray
slf4j-api/src/main/java/org/slf4j/helpers/MessageFormatter.java