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: write_dense.rs
    path of file: ./repos/mail-server/crates/store/src/backend/postgres
    
    the code of the file until where you have to start completion: /*
 * Copyright (c) 2023 Stalwart Labs Ltd.
 *
 * This file is part of the Stalwart Mail Server.
 *
 * This program is free software: you can redistribute it and/or mo
    
    pub(crate) async fn delete_range(&self, from: impl Key, to: impl Key) -> crate::Result<()> {
        let conn = self.conn_pool.get().await?;

        let s = conn
            .prepare_cached(&format!(
                "DELETE FROM {} WHERE k >= $1 AND k < $2",
                char::from(from.subspace()),
            ))
            .await?;
        conn.execute(&s, &[&from.serialize(0), &to.serialize(0)])
            .await
            .map(|_| ())
            .map_err(Into::into)
    }