code: def _find_usage_security_groups(self):
          
          vpc_count = 0
  
          paginator = self.conn.get_paginator('describe_db_security_groups')
          for page in paginator.paginate():
              for group in page['DBSecurityGroups']:
                  if 'VpcId' in group and group['VpcId'] is not None:
                      vpc_count += 1
                  self.limits['Max auths per security group']._add_current_usage(
                      len(group["EC2SecurityGroups"]) + len(group["IPRanges"]),
                      aws_type='AWS::RDS::DBSecurityGroup',
                      resource_id=group['DBSecurityGroupName']
                  )
  
          self.limits['VPC Security Groups']._add_current_usage(
              vpc_count,
              aws_type='AWS::RDS::DBSecurityGroup',
          )
docs: find usage for security groups