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: exchange_variant_bulk_updater.rb
    path of file: ./repos/openfoodnetwork/app/services
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

class ExchangeVariantBulkUpdater
  def initialize(exc
    
  def update!(variant_ids)
    sanitized_variant_ids = variant_ids.map(&:to_i).uniq
    existing_variant_ids = @exchange.variant_ids

    disassociate_variants!(existing_variant_ids - sanitized_variant_ids)
    associate_variants!(sanitized_variant_ids - existing_variant_ids)

    uncache_variant_associations
  end