import java.util.List;
import java.util.ArrayList;

public class Solution {
    public List<Object> flattenOneLevel(List<Object> array) {

        if (array == null || array.isEmpty()) {
            return new ArrayList<>();
        }

        List<Object> result = new ArrayList<>();

        for (Object obj : array) {
            if (obj instanceof List<?> nestedList) {
                for (Object nestedObject : nestedList) {
                    result.add(nestedObject);
                }
            } else {
                result.add(obj);
            }
            
        }
        
        return result;
    }
}