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: one_of_directive.rs
    path of file: ./repos/grafbase/engine/crates/parser-sdl/src/rules
    
    the code of the file until where you have to start completion: use std::vec;

use engine::{
    indexmap::IndexMap,
    registry::{InputObjectType, MetaDirective, MetaInputValue, __DirectiveLocation},
};
use engine_parser::types::TypeKind;
use if_ch
    
fn test_not_usable_on_nullable_fields() {
    use engine::registry::MetaType;
    use engine_parser::parse_schema;

    use super::visitor::{visit, VisitorContext};

    let schema = r"
        input UserByInput @oneOf {
            id: ID
            email: String
            name: String
        }
    ";

    let schema = parse_schema(schema).unwrap();
    let mut ctx = VisitorContext::new_for_tests(&schema);
    visit(&mut OneOfDirective, &mut ctx, &schema);
    assert!(ctx
        .registry
        .get_mut()
        .directives
        .iter()
        .any(|directive| directive.1.name == "oneOf"));
    assert!(ctx
        .registry
        .get_mut()
        .types
        .values()
        .any(|r#type| matches!(r#type, MetaType::InputObject(InputObjectType { oneof: true, .. }))));
}