code: static boolean isUnsupportedExpectation(HttpMessage message) {
          if (!isExpectHeaderValid(message)) {
              return false;
          }
  
          final String expectValue = message.headers().get(HttpHeaderNames.EXPECT);
          return expectValue != null && !HttpHeaderValues.CONTINUE.toString().equalsIgnoreCase(expectValue);
      }
docs: Returns {@code true} if the specified message contains an expect header specifying an expectation that is not
  supported. Note that this method returns {@code false} if the expect header is not valid for the message
  (e.g., the message is a response, or the version on the message is HTTP/1.0).
  
  @param message the message
  @return {@code true} if and only if an expectation is present that is not supported