lib/onix/apa_product.rb
def identifier_set(type, value)
      isbn_id = identifier(type)

      # create a new isbn record if we need to
      if isbn_id.nil?
        isbn_id = ONIX::ProductIdentifier.new
        isbn_id.product_id_type = type
        product.product_identifiers << isbn_id
      end

      isbn_id.id_value = value
    end
def identifier_set(type, value)
      isbn_id = identifier(type)

      # create a new isbn record if we need to
      if isbn_id.nil?
        isbn_id = ONIX::ProductIdentifier.new
        isbn_id.product_id_type = type
        product.product_identifiers << isbn_id
      end

      isbn_id.id_value = value
    end
set the value of a particular ID