code: public final void setValues(@Nullable final Set<String> values) {
          if (values != null && !values.equals(this.values)) {
              this.values = values;
              persistSet(this.values);
              notifyChanged();
          }
      }
docs: Sets the current values of the preference. By setting values, they will be persisted.
  
  @param values
  A set, which contains the values, which should be set, as an instance of the type
  {@link Set}