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/sea-query/sea-query-derive/src
    
    the code of the file until where you have to start completion: use std::convert::{TryFrom, TryInto};

use heck::ToSnakeCase;
use proc_macro::{self, TokenStream};
use quote::{quote, quote_spanned};
use syn::{parse_macro_input, Attribute, DataEnum, DataStruct, DeriveInput, Fields, Variant};

mod error;
mod iden_attr;
mod iden_path;
mod iden_variant;

use self::{
    error::ErrorMsg,
    iden_attr::IdenAttr,
    iden_path::IdenPath,
    iden_variant::{DeriveIden, DeriveIdenStatic, IdenVariant},
};

fn find_attr(attrs: &[Attribute]) -> Option<&Attribute> {
    attrs.iter().find(|attr| {
        attr.path().is_ident(&IdenPath::Iden) || attr.path().is_ident(&IdenPath::Method)
    })
}

fn get_table_name(ident: &proc_macro2::Ident, attrs: Vec<Attribute>) -> Result<String, syn::Error> {
    let table_name = match find_attr(&attrs) {
        Some(att) => match att.try_into()? {
            IdenAttr::Rename(lit) => lit,
            _ => retu
    
pub fn derive_iden(input: TokenStream) -> TokenStream {
    let DeriveInput {
        ident, data, attrs, ..
    } = parse_macro_input!(input);
    let table_name = match get_table_name(&ident, attrs) {
        Ok(v) => v,
        Err(e) => return e.to_compile_error().into(),
    };

    // Currently we only support enums and unit structs
    let variants =
        match data {
            syn::Data::Enum(DataEnum { variants, .. }) => variants,
            syn::Data::Struct(DataStruct {
                fields: Fields::Unit,
                ..
            }) => return impl_iden_for_unit_struct(&ident, &table_name).into(),
            _ => return quote_spanned! {
                ident.span() => compile_error!("you can only derive Iden on enums or unit structs");
            }
            .into(),
        };

    if variants.is_empty() {
        return TokenStream::new();
    }

    let output = impl_iden_for_enum(&ident, &table_name, variants.iter());

    output.into()
}