@Override
            public ParseResult parseUriPath(String uriPath) {
              checkArgument(
                  uriPath.matches("^/[/$!].*"),
                  "uriPath (%s) must start with // or /$ or /!",
                  uriPath);
              return parsePath(uriPath.substring(1)); // skip leading /
            }
This path service is for unix-like paths, with the exception that it recognizes $ and ! as
roots in addition to /, allowing for up to three roots. When creating a {@linkplain
PathType#toUriPath URI path}, we prefix the path with / to differentiate between a path like
"$foo/bar" and one like "/$foo/bar". They would become "/$foo/bar" and "//$foo/bar"
respectively.
jimfs/src/test/java/com/google/common/jimfs/FileTreeTest.java