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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def _validate_cert_format(name):
    '''
    Ensure that the certificate format, as determind from user input, is valid.
    '''
    cert_formats = ['cer', 'pfx']

    if name not in cert_formats:
        message = ("Invalid certificate format '{0}' specified. Valid formats:"
                   ' {1}').format(name, cert_formats)
        raise SaltInvocationError(message)