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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 order_book(self, group=True, base="btc", quote="usd"):
 """ Returns dictionary with "bids" and "asks". Each is a list of open orders and each order is represented as a list of price and amount. """

        params = {'group': group}
        url = self._construct_url("order_book/", base, quote)
        return self._get(url, params=params, return_json=True, version=2)