static boolean isValidBranchOrLeafPart(final String branchPart) {
        if (branchPart != null) {
            final int len = branchPart.length();
            if (len % 3 == 0) {
                boolean isAllNumeric = true;
                for (int i = 0; i < len; i++) {
                    final char chr = branchPart.charAt(i);
                    if (!Character.isDigit(chr)) {
                        isAllNumeric = false;
                        break;
                    }
                }
                return isAllNumeric;
            } else {
                return false;
            }
        } else {
            return false;
        }
    }
@return True if the part of a path is a valid branch part when view in isolation
i.e. ignoring other path parts. A valid branch part may also be a valid leaf
part for leaf parts of length 3.
stroom-proxy/stroom-proxy-app/src/main/java/stroom/proxy/app/handler/DirUtil.java