class Aws::Partitions::PartitionList

def partition(partition_name)
  if @partitions.key?(partition_name)
    @partitions[partition_name]
  else
    msg = "invalid partition name #{partition_name.inspect}; valid "
    msg << "partition names include %s" % [@partitions.keys.join(', ')]
    raise ArgumentError, msg
  end
end