def gen_certificate(**kwargs):
    """Generate a response to describe_certificate."""
    data = {
        'CertificateArn': kwargs.pop('CertificateArn'),
        'DomainName': 'place_holder_domain_name',
        # 'SubjectAlternativeNames': [],
        # 'DomainValidationOptions': []
    }
    data.update(kwargs)
    return {'Certificate': data}