Upgrade the plugin.

            Args:
                remote (string): Remote reference to upgrade to. The
                    ``:latest`` tag is optional and is the default if omitted.
                    Default: this plugin's name.

            Returns:
                A generator streaming the decoded API logs

def upgrade(self, remote=None):
        """
            Upgrade the plugin.

            Args:
                remote (string): Remote reference to upgrade to. The
                    ``:latest`` tag is optional and is the default if omitted.
                    Default: this plugin's name.

            Returns:
                A generator streaming the decoded API logs
        """
        if self.enabled:
            raise errors.DockerError(
                'Plugin must be disabled before upgrading.'
            )

        if remote is None:
            remote = self.name
        privileges = self.client.api.plugin_privileges(remote)
        for d in self.client.api.upgrade_plugin(self.name, remote, privileges):
            yield d
        self._reload()