You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: lib.rs
    path of file: ./repos/flutter_rust_bridge/frb_macros/src
    
    the code of the file until where you have to start completion: //! Main documentation is in https://github.com/fzyzcjy/flutter_rust_bridge

use proc_macro::*;

/// Attribute to guide code generation.
///
/// For what it can do, have a look at the documentation website.
// This is surely executed - otherwise how can one use any `#[frb]` macro
// but coverage tool does not think so, possibly because it is done in build time
// frb-coverage:ignore-start
#[proc_macro_attribute]
pub fn frb(attribute: TokenStream, item: TokenStream) -> TokenStream {
    let mut output = format_frb_attribute(format!("#[frb({attribute})]"));
    let item = strip_frb_attr(item);
    output.extend(item);
    output
}

fn strip_frb_attr(item: TokenStream) -> TokenStream {
    item.into_iter()
        .scan(None, |pound, tok| {
            use TokenTree as TT;
            match (&pound, &tok) {
                (None, TT::Punct(punct)) if punct.as_char() == '
    
fn strip_frb_attr(item: TokenStream) -> TokenStream {
    item.into_iter()
        .scan(None, |pound, tok| {
            use TokenTree as TT;
            match (&pound, &tok) {
                (None, TT::Punct(punct)) if punct.as_char() == '#' => {
                    *pound = Some(tok);
                    Some(TokenStream::new())
                }
                (Some(_), TT::Group(group)) if is_frb_bracket(group) => {
                    _ = pound.take();
                    Some(format_frb_attribute(format!("#[{}]", group.stream())))
                }
                (_, TT::Group(group)) => Some(
                    [
                        pound.take(),
                        Some(TT::Group(Group::new(
                            group.delimiter(),
                            strip_frb_attr(group.stream()),
                        ))),
                    ]
                    .into_iter()
                    .flatten()
                    .collect(),
                ),
                _ => Some(tok.into()),
            }
        })
        .collect()
}