private boolean validNumericIndex(String s) {
        if (s.isEmpty() || ((s.length() > 1) && (s.charAt(0) == '0'))) {
            return false;
        }
        
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            if (!Character.isDigit(c)) {
                return false;
            }
        }
        
        return true;
    }
Creates a label cache.

@param lockStripes number of lock stripes, should be proportional to the number of threads using the cache.
@param smallIndexSize size of a cache used to store pre-computed labels for small index labels.
vespajlib/src/main/java/com/yahoo/tensor/impl/LabelCache.java