code: @Override
    public String getHeaderField(String key) {
      try {
        getResponse();
        return getHeaderFieldDoNotForceResponse(key);
      } catch(IOException e) {
        return null;
      }
    }
docs: Returns the value of the named header field.
  
  If called on a connection that sets the same header multiple times with
  possibly different values, only the last value is returned.