code: public static File getPathtoRootmap(final URI traceFilename, final URI inputMap) {
          assert traceFilename.isAbsolute();
          assert inputMap.isAbsolute();
          return toFile(getRelativePath(traceFilename, inputMap)).getParentFile();
      }
docs: Get path to root map
  
  @param traceFilename absolute input file
  @param inputMap      absolute path to start file
  @return path to base directory, {@code null} if not available