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: guard.rs
    path of file: ./repos/holochain/crates/holochain_sqlite/src/db
    
    the code of the file until where you have to start completion: use crate::db::conn::PCon
    
    fn drop(&mut self) {
        // TODO record histogram rather than logging a warning on a fixed threshold
        let elapsed_millis = self.1.elapsed().as_millis();
        if elapsed_millis > 50 {
            tracing::warn!("PTxnGuard was held for {:?}ms", elapsed_millis);
        }
    }