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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 list_certs(self, method='all'):
 """List all certificates. :param string method: The type of certificates to list. Options are 'all', 'expired', and 'valid'. :returns: A list of dictionaries representing the requested SSL certs. Example:: # Get all valid SSL certs certs = mgr.list_certs(method='valid') print certs """

        ssl = self.client['Account']
        methods = {
            'all': 'getSecurityCertificates',
            'expired': 'getExpiredSecurityCertificates',
            'valid': 'getValidSecurityCertificates'
        }

        mask = "mask[id, commonName, validityDays, notes]"
        func = getattr(ssl, methods[method])
        return func(mask=mask)