book: updates visibility example code

book/src/visibility.md

diff --git a/book/src/visibility.md b/book/src/visibility.md
index ac0aac1..c85ab27 100644
--- a/book/src/visibility.md
+++ b/book/src/visibility.md
@@ -23,15 +23,24 @@
 Then in Rust:
 
 ```rust
-# #[repr(C)]
-# pub struct OneFieldPrivate {
-#     s: *const ::std::os::raw::c_char,
-#     pub b: bool,
-# }
-
 impl OneFieldPrivate {
     pub fn new(s: &'static std::ffi::CStr, b: bool) -> Self {
         OneFieldPrivate { s: s.as_ptr(), b }
     }
 }
+
+// generated by bindgen
+#[repr(C)]
+pub struct OneFieldPrivate {
+    s: *const ::std::os::raw::c_char,
+    pub b: bool,
+}
+
+// generated by bindgen
+#[repr(C)]
+pub struct MostFieldsPrivate {
+    a: ::std::os::raw::c_int,
+    b: bool,
+    pub c: ::std::os::raw::c_char,
+}
 ```