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: item.rs
    path of file: ./repos/gdnative/gdnative-derive/src/variant/attr
    
    the code of the file until where you have to start completion: use std::iter::FromIterator;

use proc_macro2::Span;
use syn::spanned::Spanned;

use crate::variant::{attr::generate_error_with_docs, repr::EnumReprKind};

use super::AttrBuilder;

#[derive(Clone, Debug)]
pub struct ItemAttr {
    pub enum_repr_kind: Option<(EnumReprKind, Span)>,
}

#[derive(Debug, Default)]
pub struct ItemAttrBuilder {
    enum_repr_
    
    fn done(mut self) -> Result<ItemAttr, syn::Error> {
        if self.errors.is_empty() {
            let enum_repr_kind = self
                .enum_repr_kind
                .map(|kind| match &*kind.to_string() {
                    "repr" => Ok((EnumReprKind::Repr, kind.span())),
                    "str" => Ok((EnumReprKind::Str, kind.span())),
                    _ => Err(syn::Error::new(
                        kind.span(),
                        "unknown enum representation, expected values: repr, str",
                    )),
                })
                .transpose()?;

            Ok(ItemAttr { enum_repr_kind })
        } else {
            let first_error = self.errors.remove(0);
            let errors = self
                .errors
                .into_iter()
                .fold(first_error, |mut errors, error| {
                    errors.combine(error);
                    errors
                });

            Err(errors)
        }
    }