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: se.rs
    path of file: ./repos/tremor-runtime/tremor-value/src/serde/value
    
    the code of the file until where you have to start completion: // Copyright 2020-2021, The Tremor Team

    
    fn serialize_map_no_string_keys() {
        let mut map = std::collections::HashMap::with_capacity(2);
        map.insert(1_u8, "foo");
        match to_value(map) {
            Err(e) => assert_eq!("Key must be a String.".to_string(), e.to_string()),
            other => fail!("Did not fail for non-string map keys, got: {:?}", other),
        }
    }