code: public Map<String, Map<String, Map<String, Map<String, ?>>>> addValidationConstraint(String type,
  			String field, Constraint c) {
  		if (StringUtils.isBlank(type) || StringUtils.isBlank(field) || c == null) {
  			return Collections.emptyMap();
  		}
  		return getEntity(invokePut(Utils.formatMessage("_constraints/{0}/{1}/{2}", type,
  				field, c.getName()), Entity.json(c.getPayload())), Map.class);
  	}
docs: Add a new constraint for a given field.
  @param type a type
  @param field a field name
  @param c the constraint
  @return a map containing all validation constraints for this type.