Hot to integrate Meta(Facebook) Audience Network binding with Admob?

Based on my understanding those are the required steps to integrated binding Audience Network:

1. Completed the Audience Network Setup
2. Integrating Facebook Audience Network with Mediation
3. Add a Network Security Configuration File

I am implementing native ads, and there is one extra step for it that I don't understand

The docs says:

Some Facebook native ad assets don't map one to one to Google native ad assets. Such assets are passed back to the publisher in a bundle in getExtras() method in NativeAd. Here's a code example showing how to extract these assets:

Bundle extras = nativeAd.getExtras();
if (extras.containsKey(FacebookAdapter.KEY_SOCIAL_CONTEXT_ASSET)) {
    String socialContext = extras.get(FacebookAdapter.KEY_SOCIAL_CONTEXT_ASSET);
    ...
}

What am I supposed to do with the socialContext? Also, it's an object and not a string.

At moment, I am getting Admobs ads, but for Meta, I am able to make binding requests and have some fill rate, but there are no impressions. All the rest is green.

In the Publisher Onboarding Debugger it shows that I don't properly integrate the impressions.