Configuration result = new MapConfiguration(new HashMap<String,Object>());
if(cmd.hasOption('B')) {
// check backends
Set<String> existing = Sets.newHashSet(Iterators.transform (backends.iterator(), new BackendIdentifierFunction()));
if(!existing.contains(cmd.getOptionValue('B'))) {
throw new ParseException("the backend " + cmd.getOptionValue('B') + " does not exist");
}
result.setProperty(LoaderOptions.BACKEND, cmd.getOptionValue('B'));