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: timezone.rs
    path of file: ./repos/aardwolf/aardwolf-models/src/sql_types
    
    the code of the file until where you have to start completion: use std::{error::Error as StdError, fmt, str::FromStr};

use chrono_tz::Tz;
use diesel::{backend::Backend, deserialize, serialize, sql_types::Text};

#[derive(AsExpression
    
    fn from_sql(bytes: <DB as Backend>::RawValue<'_>) -> deserialize::Result<Self> {
        deserialize::FromSql::<Text, DB>::from_sql(bytes).and_then(|string: String| {
            string
                .parse::<Timezone>()
                .map_err(|e| Box::new(e) as Box<dyn StdError + Send + Sync>)
        })
    }