AWSTemplateFormatVersion: '2010-09-09'
Conditions:
  Cond1: !Or [!Equals [sg-mysggroup, !Ref ASecurityGroup], !Condition SomeOtherCondition]
Resources:
  ClientSecurityGroup:
    Type: 'AWS::EC2::SecurityGroup'
    Properties:
      GroupDescription: !Ref 'AWS::StackName'
      VpcId: {'Fn::ImportValue': !Sub '${ParentVPCStack}-VPC'}