code: public final void setValue(@Nullable final String value) {
          if (!TextUtils.equals(this.value, value)) {
              this.value = value;
              persistString(value);
              notifyChanged();
          }
      }
docs: Sets the current value of the preference. By setting a value, it will be persisted.
  
  @param value
  The value, which should be set, as a {@link String}