code: @ExperimentalApi("https://github.com/grpc/grpc-java/issues/4683")
    public static Metadata trailersFromThrowable(Throwable t) {
      Throwable cause = checkNotNull(t, "t");
      while (cause != null) {
        if (cause instanceof StatusException) {
          return ((StatusException) cause).getTrailers();
        } else if (cause instanceof StatusRuntimeException) {
          return ((StatusRuntimeException) cause).getTrailers();
        }
        cause = cause.getCause();
      }
      return null;
    }
docs: Extract an error trailers from the causal chain of a {@link Throwable}.
  
  @return the trailers or {@code null} if not found.