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: check_placeholders_worker.rb
    path of file: ./repos/texterify/app/workers
    
    the code of the file until where you have to start completion: # Checks the translations of a project for placeholder issues.
# Missing placeholders which are available in the source
# translation but not in the other ones are
    
  def perform(background_job_id, project_id)
    background_job = BackgroundJob.find(background_job_id)
    background_job.start!
    background_job.progress!(20)

    project = Project.find(project_id)

    project.keys.each { |key| key.check_placeholders }

    background_job.complete!
  end