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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 urlscreenshot(self, external_url, agent=None, mode=None, width=None, height=None, delay=None):
 """ Takes a 'screenshot' of the given URL *returns* [Filestack.Transform] ```python from filestack import Client client = Client("API_KEY") # returns a Transform object screenshot = client.url_screenshot('https://www.example.com', width=100, height=100, agent="desktop") filelink = screenshot.store() ```` """

        params = locals()
        params.pop('self')
        params.pop('external_url')

        params = {k: v for k, v in params.items() if v is not None}

        url_task = utils.return_transform_task('urlscreenshot', params)

        new_transform = filestack.models.Transform(apikey=self.apikey, security=self.security, external_url=external_url)
        new_transform._transformation_tasks.append(url_task)

        return new_transform