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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 reload_instance(self, instance_id, post_uri=None, ssh_keys=None, image_id=None):
 """Perform an OS reload of an instance. :param integer instance_id: the instance ID to reload :param string post_url: The URI of the post-install script to run after reload :param list ssh_keys: The SSH keys to add to the root user :param int image_id: The GUID of the image to load onto the server .. warning:: This will reformat the primary drive. Post-provision script MUST be HTTPS for it to be executed. Example:: # Reload instance ID 12345 then run a custom post-provision script. # Post-provision script MUST be HTTPS for it to be executed. post_uri = 'https://somehost.com/bootstrap.sh' vsi = mgr.reload_instance(12345, post_uri=post_url) """

        config = {}

        if post_uri:
            config['customProvisionScriptUri'] = post_uri

        if ssh_keys:
            config['sshKeyIds'] = [key_id for key_id in ssh_keys]

        if image_id:
            config['imageTemplateId'] = image_id

        return self.client.call('Virtual_Guest', 'reloadOperatingSystem',
                                'FORCE', config, id=instance_id)