public void setDefaultFontFileExtension(String extension) {
    defaultFontFileExtension = extension;
    FontAssetManager fam = getFontAssetManager();
    if (fam != null) {
      fam.setDefaultFontFileExtension(extension);
    }
  }
By default, Lottie will look in src/assets/fonts/FONT_NAME.ttf
where FONT_NAME is the fFamily specified in your Lottie file.
If your fonts have a different extension, you can override the
default here.
<p>
Alternatively, you can use {@link #setFontAssetDelegate(FontAssetDelegate)}
for more control.

@see #setFontAssetDelegate(FontAssetDelegate)
lottie/src/main/java/com/airbnb/lottie/LottieDrawable.java