code: @CheckResult @NonNull
    public Preference<Float> getFloat(@NonNull String key, @NonNull Float defaultValue) {
      checkNotNull(key, "key == null");
      checkNotNull(defaultValue, "defaultValue == null");
      return new RealPreference<>(preferences, key, defaultValue, FloatAdapter.INSTANCE, keyChanges);
    }
docs: Create a float preference for {@code key} with a default of {@code defaultValue}.