code: public Optional<Long> getDuration(final String path, final TimeUnit unit) {		
  		return config.hasPath(requireNonNull(path, "A non-null path expected")) 
  				? ofNullable(config.getDuration(path, requireNonNull(unit, "A non-null unit expected"))) : empty();
  	}
docs: Description copied from the method {@link Config#getDuration(String, TimeUnit)}: Gets a value as a duration in a specified TimeUnit. If the value
  is already a number, then it's taken as milliseconds and then converted to the requested TimeUnit; if it's a string, it's parsed understanding
  units suffixes like "10m" or "5ns" as documented in <a href="https://github.com/typesafehub/config/blob/master/HOCON.md">the spec</a>.
  @param path - path expression
  @param unit - convert the return value to this time unit
  @return the duration value at the requested path, in the given TimeUnit