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: builder.rs
    path of file: ./repos/wasmer/lib/compiler/src/engine
    
    the code of the file until where you have to start completion: use super::Engine;
use crate::CompilerConfig;
use wasmer_types::{Features, Target};

/// The Builder contents of `Engine`
pub struct EngineBuilder {
    /// The compiler
    compiler_config: Option<Box<dyn CompilerConfig>>,
    /// The machine target
    target: Option<Target>,
    /// The features 
    
    pub fn engine(self) -> Engine {
        let target = self.target.unwrap_or_default();
        if let Some(compiler_config) = self.compiler_config {
            let features = self
                .features
                .unwrap_or_else(|| compiler_config.default_features_for_target(&target));
            Engine::new(compiler_config, target, features)
        } else {
            Engine::headless()
        }
    }