OQL to query nested Objects

My object structure is as below:

Class A

{

   public string key;

   public string fieldName;

   List<ArrayList<MyCustomObject>> myNewObject = new ArrayList<ArrayList<MyCustomObject>>();

}

Class MyCustomObject

{

public String key;

public String value

}

Now I want to write a OQL on this object, how do I write a query "key"= 1. 

Select ernfrom /ExampleRegion er, er.myNewObject ern

This will return ArrayList<MyCustomObject>

How do I write ern.items."key"= "mykeyToCompare"

Any solution to this issue.