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: test_signature.rs
    path of file: ./repos/nushell/crates/nu-protocol/tests
    
    the code of the file until where you have to start completion: use nu_protocol::{Flag, PositionalArg, Signature, SyntaxShape};

#[test]
fn test_sign
    
fn test_signature_round_trip() {
    let signature = Signature::new("new_signature")
        .usage("description")
        .required("first", SyntaxShape::String, "first required")
        .required("second", SyntaxShape::Int, "second required")
        .optional("optional", SyntaxShape::String, "optional description")
        .required_named(
            "req-named",
            SyntaxShape::String,
            "required named description",
            Some('r'),
        )
        .named("named", SyntaxShape::String, "named description", Some('n'))
        .switch("switch", "switch description", None)
        .rest("rest", SyntaxShape::String, "rest description")
        .category(nu_protocol::Category::Conversions);

    let string = serde_json::to_string_pretty(&signature).unwrap();
    let returned: Signature = serde_json::from_str(&string).unwrap();

    assert_eq!(signature.name, returned.name);
    assert_eq!(signature.usage, returned.usage);
    assert_eq!(signature.extra_usage, returned.extra_usage);
    assert_eq!(signature.is_filter, returned.is_filter);
    assert_eq!(signature.category, returned.category);

    signature
        .required_positional
        .iter()
        .zip(returned.required_positional.iter())
        .for_each(|(lhs, rhs)| assert_eq!(lhs, rhs));

    signature
        .optional_positional
        .iter()
        .zip(returned.optional_positional.iter())
        .for_each(|(lhs, rhs)| assert_eq!(lhs, rhs));

    signature
        .named
        .iter()
        .zip(returned.named.iter())
        .for_each(|(lhs, rhs)| assert_eq!(lhs, rhs));

    assert_eq!(signature.rest_positional, returned.rest_positional,);
}