code: @SuppressWarnings("unchecked")
      public final V getIfExists() {
          InternalThreadLocalMap threadLocalMap = InternalThreadLocalMap.getIfSet();
          if (threadLocalMap != null) {
              Object v = threadLocalMap.indexedVariable(index);
              if (v != InternalThreadLocalMap.UNSET) {
                  return (V) v;
              }
          }
          return null;
      }
docs: Returns the current value for the current thread if it exists, {@code null} otherwise.