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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 client_factory(self):
 """ Custom client factory to set proxy options. """

        
        if self._service.production:
            url = self.production_url
        else:
            url = self.testing_url
        
        proxy_options = dict()
        https_proxy_setting = os.environ.get('PAYEX_HTTPS_PROXY') or os.environ.get('https_proxy')
        http_proxy_setting = os.environ.get('PAYEX_HTTP_PROXY') or os.environ.get('http_proxy')
        
        if https_proxy_setting:
            proxy_options['https'] = https_proxy_setting
        if http_proxy_setting:
            proxy_options['http'] = http_proxy_setting
        
        return client.Client(url, proxy=proxy_options)