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: weak.rs
    path of file: ./repos/y-crdt/ywasm/src
    
    the code of the file until where you have to start completion: use crate::collection::SharedCollection;
use crate::js::Js;
use crate::transaction::YTransaction;
use crate::{ImplicitTransaction, Observer, Result};
use std::sync::Arc;
use wasm_bindgen::prelude::wasm_bindgen;
use wasm_bindgen::JsValue;
use yrs::branch::BranchPtr;
use yrs::types::weak::{LinkSource, WeakEvent};
use yrs::ty
    
    pub fn deref(&self, txn: &ImplicitTransaction) -> Result<JsValue> {
        use yrs::MapRef;

        match &self.0 {
            SharedCollection::Prelim(c) => {
                let weak_ref: WeakPrelim<MapRef> = WeakPrelim::from(c.prelim.clone());
                let value = match YTransaction::from_implicit(txn)? {
                    Some(txn) => {
                        let txn: &TransactionMut = &*txn;
                        weak_ref.try_deref_raw(txn)
                    }
                    None => {
                        let txn = c
                            .doc
                            .try_transact()
                            .map_err(|_| JsValue::from_str(crate::js::errors::ANOTHER_RW_TX))?;
                        weak_ref.try_deref_raw(&txn)
                    }
                };
                match value {
                    None => Ok(JsValue::UNDEFINED),
                    Some(value) => Ok(Js::from_value(&value, &c.doc).into()),
                }
            }
            SharedCollection::Integrated(c) => c.readonly(txn, |c, txn| {
                let weak_ref: WeakRef<MapRef> = WeakRef::from(c.clone());
                let value = weak_ref.try_deref_value(txn);
                match value {
                    None => Ok(JsValue::UNDEFINED),
                    Some(value) => Ok(Js::from_value(&value, txn.doc()).into()),
                }
            }),
        }
    }