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: history.rs
    path of file: ./repos/fish-shell/src
    
    the code of the file until where you have to start completion: //! Fish supports multiple shells writing to history at once. Here is its strategy:
//!
//! 1. All history files are append-only. Data, once written, is never modified.
//!
//! 2. A history file may be re-written ("vacuumed"). This involves reading in the file and writing a
//! new one, while performing maintenance tasks: discarding items in an LRU fashion until we reach
//! the desired maximum count, r
    
    fn set_valid_file_paths(&mut self, valid_file_paths: Vec<WString>, ident: HistoryIdentifier) {
        // 0 identifier is used to mean "not necessary".
        if ident == 0 {
            return;
        }

        // Look for an item with the given identifier. It is likely to be at the end of new_items.
        for item in self.new_items.iter_mut().rev() {
            if item.identifier == ident {
                // found it
                item.required_paths = valid_file_paths;
                break;
            }
        }
    }