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: mod.rs
    path of file: ./repos/mundane/src/public/rsa
    
    the code of the file until where you have to start completion: // Copyright 2018 Google LLC
//
// Use of this source code is governed by an MIT-style
// license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT.

//! The RSA public-key cryptosystem.

mod bits;

pub use public::rsa::bits::{RsaKeyBits, B2048, B3072, B4096, B6144, B8192};

use std::fmt::{self, Debug, Display, Formatter};
use std::marker::PhantomData;

use boringssl::{self, BoringError, CHeapWrapper, CStackWrapper};
use hash::{inner::Digest, Hashe
    
        pub fn public_modulus_be(&self) -> Vec<u8> {
            // Guaranteed to succeed because RSA_get0_n can only fail if
            // the "n" parameter is not initialized, but one of the invariants
            // on RsaKey is that it is initialized.
            let bignum = self.key.rsa_get0_n().unwrap();
            let num_bytes = bignum.bn_num_bytes();
            let mut modulus = vec![0; num_bytes];
            // Guaranteed to succeed because the size of `modulus` is
            // [`bn_num_bytes`].
            bignum.bn_bn2bin_padded(modulus.as_mut_slice()).unwrap();

            modulus
        }