code: public Config setUserContext(ConcurrentMap<String, Object> userContext) {
          if (userContext == null) {
              throw new IllegalArgumentException("userContext can't be null");
          }
          this.userContext = userContext;
          return this;
      }
docs: Sets the user supplied context. This context can then be obtained
  from an instance of {@link com.hazelcast.core.HazelcastInstance}.
  
  @param userContext the user supplied context
  @return this config instance
  @see HazelcastInstance#getUserContext()