public Set<String> getGroups() {
		Set<String> groupSet;
		String groups = this.get(GROUPS_KEY);
		groupSet = StringUtils.hasText(groups) ? StringUtils.commaDelimitedListToSet(groups) : new HashSet<String>();
		return Collections.unmodifiableSet(groupSet);
	}
Constructor to be called when the attributes are already known. If an id is not present in the map, one will be
generated.

@param attributes the container's attributes
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/cluster/ContainerAttributes.java