code: func (ec2i *FakeEC2Impl) DescribeVpcs(request *ec2.DescribeVpcsInput) (*ec2.DescribeVpcsOutput, error) {
  	return &ec2.DescribeVpcsOutput{Vpcs: []*ec2.Vpc{{CidrBlock: aws.String("172.20.0.0/16")}}}, nil
  }
docs: // DescribeVpcs returns fake VPC descriptions