def txn_read_preference
      rp = txn_options && txn_options[:read_preference] ||
        @client.read_preference
      Mongo::Lint.validate_underscore_read_preference(rp)
      rp
    end
def txn_read_preference
      rp = txn_options && txn_options[:read_preference] ||
        @client.read_preference
      Mongo::Lint.validate_underscore_read_preference(rp)
      rp
    end
Get the read preference the session will use in the currently
 active transaction.

 This is a driver style hash with underscore keys.

 @example Get the transaction's read preference
   session.txn_read_preference

 @return [ Hash ] The read preference of the transaction.

 @since 2.6.0