text: from checkov.common.models.enums import CheckResult, CheckCategories
  from checkov.common.util.type_forcers import force_int
  from checkov.terraform.checks.resource.base_resource_check import BaseResourceCheck
  from typing import List
  
  
  class DBInstanceBackupRetentionPeriod(BaseResourceCheck):
      def __init__(self):
          name = "Ensure that RDS instances has backup policy"
          id = "CKV_AWS_133"
          supported_resources = ['aws_rds_cluster','aws_db_instance']
          categories = [CheckCategories.BACKUP_AND_RECOVERY]
          super().__init__(name=name, id=id, categories=categories, supported_resources=supported_resources)
  
      def scan_resource_conf(self, conf):
          key = "backup_retention_period"
          if key in conf.keys():
              period = conf[key][0]
              if self._is_variable_dependant(period):
                  return CheckResult.UNKNOWN
              period = force_int(period)
              if period and 0 < period <= 35:
                  return CheckResult.PASSED
              return CheckResult.FAILED
          # Default value is 1 which passes ^^^
          return CheckResult.PASSED
  
      def get_evaluated_keys(self) -> List[str]:
          return ['backup_retention_period']
  
  
  check = DBInstanceBackupRetentionPeriod()
  