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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 marginBuy(self, currencyPair, rate, amount, lendingRate=None):
 """Places a margin buy order in a given market. Required POST parameters are "currencyPair", "rate", and "amount". You may optionally specify a maximum lending rate using the "lendingRate" parameter. If successful, the method will return the order number and any trades immediately resulting from your order."""

        return self._private('marginBuy', currencyPair=currencyPair, rate=rate,
                             amount=amount, lendingRate=lendingRate)