code: public boolean isXForwardedHeaderRequired() {
          return forwardedHeader == null && (xForwardedForHeader != null || xForwardedByHeader != null ||
                  xForwardedHostHeader != null || xForwardedProtoHeader != null);
      }
docs: Check header values and return true if X-Forwarded-- headers need to be set. X-Forwarded-- headers are set,
  when only the X-Forwarded-- headers are present.
  
  @return a boolean to denote the required header