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: directlighting.rs
    path of file: ./repos/rs_pbrt/src/integrators
    
    the code of the file until where you have to start completion: // std
use std::sync::Arc;
// pbrt
use crate::core::camera::Camera;
use crate::core::geometry::{vec3_abs_dot_nrmf, vec3_dot_nrmf};
use crate::core::geometry::{Bounds2i, Normal3f, Ray, RayDifferential, Vector3f};
use crate
    
    pub fn preprocess(&mut self, scene: &Scene) {
        if self.strategy == LightStrategy::UniformSampleAll {
            // compute number of samples to use for each light
            for li in 0..scene.lights.len() {
                let light = &scene.lights[li];
                self.n_light_samples
                    .push(self.sampler.round_count(light.get_n_samples()));
            }
            // request samples for sampling all lights
            for _i in 0..self.max_depth {
                for j in 0..scene.lights.len() {
                    self.sampler.request_2d_array(self.n_light_samples[j]);
                    self.sampler.request_2d_array(self.n_light_samples[j]);
                }
            }
        }
    }