code: private Constraint putToCache(final String id, final Constraint object) {
  		Constraint c = this.map.put(id, object);
  		if (c instanceof DummyConstraint) {
  			((DummyConstraint) c).constraint = object;
  			return null;
  		}
  		return c;
  	}
docs: Puts the given constraint object into the cache using the key id. If an existing
  DummyConstraint object is found in the table, the reference will be set to the constraint and
  the constraint will not be put into the table.