    # File lib/fog/aws/elasticache.rb, line 148
            def initialize(options={})
              @aws_credentials_expire_at = Time::now + 20
              setup_credentials(options)
              @region = options[:region] || 'us-east-1'
              unless ['ap-northeast-1', 'ap-southeast-1', 'eu-west-1', 'us-east-1',
                      'us-west-1', 'us-west-2', 'sa-east-1'].include?(@region)
                raise ArgumentError, "Unknown region: #{@region.inspect}"
              end
            end