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: crypto_expressions.rs
    path of file: ./repos/arrow-datafusion/datafusion/physical-expr/src
    
    the code of the file until where you have to start completion: // Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// 
    
pub fn md5(args: &[ColumnarValue]) -> Result<ColumnarValue> {
    if args.len() != 1 {
        return exec_err!(
            "{:?} args were supplied but {} takes exactly one argument",
            args.len(),
            DigestAlgorithm::Md5
        );
    }
    let value = digest_process(&args[0], DigestAlgorithm::Md5)?;
    // md5 requires special handling because of its unique utf8 return type
    Ok(match value {
        ColumnarValue::Array(array) => {
            let binary_array = as_binary_array(&array)?;
            let string_array: StringArray = binary_array
                .iter()
                .map(|opt| opt.map(hex_encode::<_>))
                .collect();
            ColumnarValue::Array(Arc::new(string_array))
        }
        ColumnarValue::Scalar(ScalarValue::Binary(opt)) => {
            ColumnarValue::Scalar(ScalarValue::Utf8(opt.map(hex_encode::<_>)))
        }
        _ => return exec_err!("Impossibly got invalid results from digest"),
    })
}