src/main/java/com/arpnetworking/steno/Logger.java
static @Nullable Throwable extractThrowable(
            @Nullable final String[] keys, 
            @Nullable final Object[] values) {
        final int keyLength = keys == null ? 0 : keys.length;
        if (values != null && values.length == keyLength + 1) {
            final int throwableIndex = values.length - 1;
            if (values[throwableIndex] instanceof Throwable) {
                return (Throwable) values[throwableIndex];
            }
        }
        return null;
    }
static @Nullable Throwable extractThrowable(
            @Nullable final String[] keys, 
            @Nullable final Object[] values) {
        final int keyLength = keys == null ? 0 : keys.length;
        if (values != null && values.length == keyLength + 1) {
            final int throwableIndex = values.length - 1;
            if (values[throwableIndex] instanceof Throwable) {
                return (Throwable) values[throwableIndex];
            }
        }
        return null;
    }
/* package private