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: static_join_to_fstring.rs
    path of file: ./repos/ruff/crates/ruff_linter/src/rules/flynt/rules
    
    the code of the file until where you have to start completion: use ast::FStringFlags;
use itertools::Itertools;

use crate::fix::edits::pad;
use ruff_diagnostics::{AlwaysFixableViolation, Diagnostic, Edit, Fix};
us
    
    fn message(&self) -> String {
        let StaticJoinToFString { expression } = self;
        if let Some(expression) = expression.full_display() {
            format!("Consider `{expression}` instead of string join")
        } else {
            format!("Consider f-string instead of string join")
        }
    }