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: transaction.rb
    path of file: ./repos/activerecord-sqlserver-adapter/lib/active_record/connection_adapters/sqlserver
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

req
    
      def current_isolation_level
        return unless connection_sqlserver?

        level = connection.user_options_isolation_level
        # When READ_COMMITTED_SNAPSHOT is set to ON,
        # user_options_isolation_level will be equal to 'read committed
        # snapshot' which is not a valid isolation level
        if level.blank? || level == "read committed snapshot"
          "READ COMMITTED"
        else
          level.upcase
        end