format

pub fn format(fet: FormatErrorTrace, writer: *std.Io.Writer) std.Io.Writer.Error!void {
        if (fet.error_trace) |ert| {
            try writer.writeByte('\n');
            try std.debug.writeErrorReturnTrace(ert, .{ .writer = writer, .mode = fet.terminal_mode });
        } else {
            try writer.writeAll("null");
        }
    }