code: private Set<String> validateAddCapabilities(final Job job) {
      final Set<String> caps = job.getAddCapabilities();
  
      if (caps == null) {
        return emptySet();
      }
  
      final Set<String> errors = Sets.newHashSet();
  
      final Set<String> disallowedCaps = Sets.difference(caps, whitelistedCapabilities);
  
      if (!disallowedCaps.isEmpty()) {
        errors.add(String.format(
            "The following Linux capabilities aren't allowed by the Helios master: '%s'. "
            + "The allowed capabilities are: '%s'.",
            Joiner.on(", ").join(disallowedCaps), Joiner.on(", ").join(whitelistedCapabilities)));
      }
  
      return errors;
    }
docs: Validate the Job's added Linux capabilities.
  
  @param job The Job to check.
  
  @return A set of error Strings