private Typeface getFontFamily(Font font) {
    String fontFamily = font.getFamily();
    Typeface defaultTypeface = fontFamilies.get(fontFamily);
    if (defaultTypeface != null) {
      return defaultTypeface;
    }

    Typeface typeface = null;
    String fontStyle = font.getStyle();
    String fontName = font.getName();
    if (delegate != null) {
      typeface = delegate.fetchFont(fontFamily, fontStyle, fontName);
      if (typeface == null) {
        typeface = delegate.fetchFont(fontFamily);
      }
    }

    if (delegate != null && typeface == null) {
      String path = delegate.getFontPath(fontFamily, fontStyle, fontName);
      if (path == null) {
        path = delegate.getFontPath(fontFamily);
      }
      if (path != null) {
        typeface = Typeface.createFromAsset(assetManager, path);
      }
    }

    if (font.getTypeface() != null) {
      return font.getTypeface();
    }

    if (typeface == null) {
      String path = "fonts/" + fontFamily + defaultFontFileExtension;
      typeface = Typeface.createFromAsset(assetManager, path);
    }

    fontFamilies.put(fontFamily, typeface);
    return typeface;
  }
Sets the default file extension (include the `.`).
<p>
e.g. `.ttf` `.otf`
<p>
Defaults to `.ttf`
lottie/src/main/java/com/airbnb/lottie/manager/FontAssetManager.java