code: public Collection<String> getAllowedMethods(String requestMethod) {
  
  		Constraint.ensureNotEmpty(requestMethod, String.format("Invalid method '%s'", requestMethod));
  		Set<String> rtAllowedMethods = new HashSet<String>(allowedMethods);
  		rtAllowedMethods.add(requestMethod.toUpperCase());
  
  		return rtAllowedMethods;
  	}
docs: Return all methods allowed by the resource, including the preflight request method
  
  @param requestMethod
  @return