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: lib.rs
    path of file: ./repos/pavex/libs/pavex_cli/tests/ui_tests/error_observers/error_observers_can_depend_on_fallible_singletons
    
    the code of the file until where you have to start completion: use pavex::blueprint::{constructor::Lifecycle, router::GET, Blueprint};
use pavex::f;
use pavex::response::Response;

#[derive(Clone)]
pub struct A;

pub struct B;

#[derive(Debug)]
pu
    
pub fn blueprint() -> Blueprint {
    let mut bp = Blueprint::new();
    bp.constructor(f!(crate::a), Lifecycle::Singleton);
    bp.constructor(f!(crate::b), Lifecycle::RequestScoped)
        .error_handler(f!(crate::error_handler));
    bp.error_observer(f!(crate::error_observer));
    bp.route(GET, "/home", f!(crate::handler));
    bp
}