c# - Read Android intent extra data on Unity app launch

Question

I am launching an Unity application from another Android application using a custom implicit intent. This is working fine, but I cannot figure out how to read the intent extra data in Unity?

ANDROID INTENT TO LAUNCH UNITY APP

i=new Intent();
i.setAction("com.company.unityapp.MyMethod");
i.putExtra("KEY","This is the message string");
startActivity(i);

UNITY APP AndroidManifest.xml

<intent-filter>
     <action android:name="com.company.unityapp.MyMethod" />
     <category android:name="android.intent.category.DEFAULT" />
</intent-filter>

I have a GameObject in my scene with a script attached. Inside the start method I have this code to try and read the extra data that was passed along with the intent

AndroidJavaClass UnityPlayer = new AndroidJavaClass("com.unity3d.player.UnityPlayer"); 
AndroidJavaObject currentActivity = UnityPlayer.GetStatic<AndroidJavaObject>("currentActivity");

AndroidJavaObject intent = currentActivity.Call<AndroidJavaObject>("getIntent");
bool hasExtra = intent.Call<bool> ("hasExtra", "arguments");

if (hasExtra) {
 AndroidJavaObject extras = intent.Call<AndroidJavaObject> ("getExtras");
 arguments = extras.Call<string> ("getString", "arguments");
}

This is not working and arguments is always empty. Any help would be appreciated.