code: public static void setContextMap(Map<String, String> contextMap) {
          if (mdcAdapter == null) {
              throw new IllegalStateException("MDCAdapter cannot be null. See also " + NULL_MDCA_URL);
          }
          mdcAdapter.setContextMap(contextMap);
      }
docs: Set the current thread's context map by first clearing any existing map and
  then copying the map passed as parameter. The context map passed as
  parameter must only contain keys and values of type String.
  
  @param contextMap
  must contain only keys and values of type String
  @since 1.5.1