code: @NonNull
      public static <T> T nonNull(@Nullable T obj) {
          if (obj == null) {
             throw new IllegalArgumentException("encountered illegal null value");
          }
          return obj;
      }
docs: Asserts that the given object is non null.
  
  @param <T> Type of the object to test.
  @param obj The object to test.
  @return The object.