def describe_ca_certificate(certificateId=None):
    """
    Describes a registered CA certificate.
    See also: AWS API Documentation
    
    
    :example: response = client.describe_ca_certificate(
        certificateId='string'
    )
    
    
    :type certificateId: string
    :param certificateId: [REQUIRED]
            The CA certificate identifier.
            

    :rtype: dict
    :return: {
        'certificateDescription': {
            'certificateArn': 'string',
            'certificateId': 'string',
            'status': 'ACTIVE'|'INACTIVE',
            'certificatePem': 'string',
            'ownedBy': 'string',
            'creationDate': datetime(2015, 1, 1),
            'autoRegistrationStatus': 'ENABLE'|'DISABLE'
        }
    }
    
    
    """
    pass
