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: x509.rs
    path of file: ./repos/deno/ext/node/ops/crypto
    
    the code of the file until where you have to start completion: // Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.

use deno_core::error::AnyError;
use deno_core::op2;
use deno_core::v8;

use x509_p
    
  fn fingerprint<D: Digest>(&self) -> Option<String> {
    self.pem.as_ref().map(|pem| {
      let mut hasher = D::new();
      hasher.update(&pem.contents);
      let bytes = hasher.finalize();
      // OpenSSL returns colon separated upper case hex values.
      let mut hex = String::with_capacity(bytes.len() * 2);
      for byte in bytes {
        hex.push_str(&format!("{:02X}:", byte));
      }
      hex.pop();
      hex
    })
  }