private Map<String, Collection<GrantedAuthority>> preProcessMap(Map<?, ?> orgMap) {
		Map<String, Collection<GrantedAuthority>> result = new HashMap<String, Collection<GrantedAuthority>>(
				orgMap.size());

		for (Map.Entry<?, ?> entry : orgMap.entrySet()) {
			Assert.isInstanceOf(String.class, entry.getKey(),
					"attributes2grantedAuthoritiesMap contains non-String objects as keys");
			result.put((String) entry.getKey(),
					getGrantedAuthorityCollection(entry.getValue()));
		}
		return result;
	}