def generate(self, url, browsers=None, orientation=None, mac_res=None, win_res=None,
                             quality=None, local=None, wait_time=None, callback_url=None):
        """
        Generates screenshots for a URL.
        """
        if isinstance(browsers, dict):
            browsers = [browsers]
        if browsers is None:
            browsers = [self.default_browser]
        data = dict((key, value) for key, value in locals().items() if value is not None and key != 'self')
        return self.execute('POST', '/screenshots', json=data)