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: 0211-design-add-and-search-words-data-structure.rs
    path of file: ./repos/NeetCode-Solutions/08_Tries/02_Design_Add_and_Search_Words_Data_Structure
    
    the code of the file until where you have to start completion: /*
Problem: LeetCode 211 - Add and Search Word - Data structure

Key Idea:
The key idea is to use a Trie data structure to efficiently store and search for words with wi
    
    pub fn add_word(&mut self, word: String) {
        let mut node = &mut self.root;
        for c in word.chars() {
            let index = (c as u8 - b'a') as usize;
            node = node.children[index].get_or_insert_with(|| Box::new(TrieNode::new()));
        }
        node.is_end = true;
    }