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/farm/crates/macro_cache_item/src
    
    the code of the file until where you have to start completion: use proc_macro::TokenStream;
use proc_macro2::Ident;
use quote::quote;
use syn::{parse_macro_input, parse_quote, Item};

#[proc_macro_attribute]
pub fn cache_item(attr: TokenStream, input: TokenStream) -> TokenStream {
  let item: Item = parse_macro_input!(input);

  if !attr.is_empty() {
    let args: Ident = parse_macro_input!(attr);

    let item_ident = match &item {
      Item::Enum(e) => e.ident.clone(),
      Item::Struct(s) => s.ident.clone(),
      _ => {
        let ts: proc_macro2::TokenStream = parse_quote! {
          compile_error!("#[cache_item] can only be used on struct or enum")
        };
        return ts.into();
      }
    };
    let derives = quote! {
      use rkyv::*;

      #[derive(rkyv::Serialize, rkyv::Deserialize, rkyv::Archive)]
      #[archive_attr(derive(TypeName))]
      #item

      #[archive_dyn(deserialize)]
      impl #args for #item_ident {}
      impl #args for rkyv::Archived<#item_ident> {}
   
    
pub fn cache_item(attr: TokenStream, input: TokenStream) -> TokenStream {
  let item: Item = parse_macro_input!(input);

  if !attr.is_empty() {
    let args: Ident = parse_macro_input!(attr);

    let item_ident = match &item {
      Item::Enum(e) => e.ident.clone(),
      Item::Struct(s) => s.ident.clone(),
      _ => {
        let ts: proc_macro2::TokenStream = parse_quote! {
          compile_error!("#[cache_item] can only be used on struct or enum")
        };
        return ts.into();
      }
    };
    let derives = quote! {
      use rkyv::*;

      #[derive(rkyv::Serialize, rkyv::Deserialize, rkyv::Archive)]
      #[archive_attr(derive(TypeName))]
      #item

      #[archive_dyn(deserialize)]
      impl #args for #item_ident {}
      impl #args for rkyv::Archived<#item_ident> {}
    };

    return derives.into();
  }

  let derives = quote! {
    use rkyv::*;

    #[derive(rkyv::Serialize, rkyv::Deserialize, rkyv::Archive)]
    #item
  };

  derives.into()
}