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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 update(self, **kwargs):
 """When setting useProxyServer to enable we need to supply proxyServerPool value as well """

        if 'useProxyServer' in kwargs and kwargs['useProxyServer'] == 'enabled':
            if 'proxyServerPool' not in kwargs:
                error = 'Missing proxyServerPool parameter value.'
                raise MissingUpdateParameter(error)
        if hasattr(self, 'useProxyServer'):
            if getattr(self, 'useProxyServer') == 'enabled' and 'proxyServerPool' not in self.__dict__:
                error = 'Missing proxyServerPool parameter value.'
                raise MissingUpdateParameter(error)

        self._update(**kwargs)

        return self