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: params.rb
    path of file: ./repos/gitlabhq/app/finders/merge_requests_finder
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

class MergeRequestsFinder
  class Params < Is
    
    def reviewer
      strong_memoize(:reviewer) do
        if reviewer_id?
          User.find_by_id(params[:reviewer_id])
        elsif reviewer_username?
          User.find_by_username(params[:reviewer_username])
        end
      end