private static void validatePart(final String part) {
        if (part == null || part.isEmpty()) {
            throw new RuntimeException("Null or empty path part");
        }
    }
Construct a {@link DocPath} from a path string, e.g. {@code /foo/bar}.
A leading {@code /} means the path is absolute. Any trailing {@code /}
will be stripped.
stroom-util-shared/src/main/java/stroom/util/shared/DocPath.java