Syncope Client 1.2.7 - Create user with plain attributes

[Santiago Moral]

Hi,
I'm Santiago Moral and I want to create a new User with plain attributes 
using de Syncope Client 1.2.7 and I can't find a way to add this 
attributes to de entity UserTO. I've tried using the following code:

AttributeTO attributeTO = new AttributeTO();
attributeTO.setSchema(schema);
attributeTO.getValues().add(value);
userTO.getAttrMap().put(attributeTO.getSchema(), attributeTO);

I'm getting java.lang.UnsupportedOperationException becouse attrMap is 
an UnmodifiableMap.

I really apreciate any kind of help that you can bring to me.

Regards,
Santiago.