public static <A, B> Pair<A, B> of(A first, B second) {
    return new Pair<A, B>(first, second);
  }
Represents a pair of two objects
@param <A> The type of the first object in the pair.
@param <B> The type of the second object in the pair.
ambry-utils/src/main/java/com/github/ambry/utils/Pair.java