    # File lib/rmail/header.rb, line 876
        def address_list_assign(field_name, addresses)
          if addresses.kind_of?(Array)
            value = addresses.collect { |e|
              if e.kind_of?(RMail::Address)
                e.format
              else
                RMail::Address.parse(e.to_str).collect { |a|
                  a.format
                }
              end
            }.flatten.join(", ")
            set(field_name, value)
          elsif addresses.kind_of?(RMail::Address)
            set(field_name, addresses.format)
          else
            address_list_assign(field_name,
                                RMail::Address.parse(addresses.to_str))
          end
        end