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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 package_list(cls, options=None):
 """ List possible certificate packages."""

        options = options or {}
        try:
            return cls.safe_call('cert.package.list', options)
        except UsageError as err:
            if err.code == 150020:
                return []
            raise