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: commit_signer.rb
    path of file: ./repos/dependabot-core/common/lib/dependabot/pull_request_creator
    
    the code of the file until where you have to start completion: # typed: strict
# frozen_string_literal: true

require "time"
require "tmpdir"
require "sorbet-runtime"
require "dependabot/pull_request_creator"

module Dependabot
  class PullRequestCreator
    class CommitSigner
      extend T::Sig

      sig { return
    
      def commit_object
        time_str = Time.parse(T.must(author_details[:date])).strftime("%s %z")
        name = author_details[:name]
        email = author_details[:email]

        [
          "tree #{tree_sha}",
          "parent #{parent_sha}",
          "author #{name} <#{email}> #{time_str}",
          "committer #{name} <#{email}> #{time_str}",
          "",
          commit_message
        ].join("\n")
      end