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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 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)