code: public static Map<String, String> getCopyOfContextMap() {
          if (mdcAdapter == null) {
              throw new IllegalStateException("MDCAdapter cannot be null. See also " + NULL_MDCA_URL);
          }
          return mdcAdapter.getCopyOfContextMap();
      }
docs: Return a copy of the current thread's context map, with keys and values of
  type String. Returned value may be null.
  
  @return A copy of the current thread's context map. May be null.
  @since 1.5.1