public void addTrait(ClassEntity trait) {
        if (!trait.isTrait())
            throw new IllegalArgumentException("'" + trait.getName() + "' is not a trait");

        this.traits.put(trait.getLowerName(), trait);
    }
return empty list if success else list with not valid implemented methods in class

@param _interface
@return
jphp-runtime/src/php/runtime/reflection/ClassEntity.java