lib/plugins/aws/package/compile/events/sns/index.js/AwsCompileSNSEvents/isValidStackImport
class AwsCompileSNSEvents:  isValidStackImport(variable) {
    if (Object.keys(variable).length !== 1) {
      return false;
    }
    if (_.has(variable, 'Fn::ImportValue') &&
      (_.has(variable, 'Fn::ImportValue.Fn::GetAtt') || _.has(variable, 'Fn::ImportValue.Ref'))) {
      return false;
    }
    const intrinsicFunctions = ['Fn::ImportValue', 'Ref', 'Fn::GetAtt', 'Fn::Sub', 'Fn::Join'];
    return !!_.find(intrinsicFunctions, func => _.has(variable, func));
  }