fieldSelectionCriteria

A filter expression that specifies which log events should be processed by this subscription filter based on system fields such as source account and source region. Uses selection criteria syntax with operators like =, !=, AND, OR, IN, NOT IN. Example: @aws.region NOT IN ["cn-north-1"] or @aws.account = "123456789012" AND @aws.region = "us-east-1". Maximum length: 2000 characters.