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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 withdraw(self, currency, amount, address, paymentId=None):
 """Immediately places a withdrawal for a given currency, with no email confirmation. In order to use this method, the withdrawal privilege must be enabled for your API key. Required POST parameters are "currency", "amount", and "address". For XMR withdrawals, you may optionally specify "paymentId"."""

        return self._private('withdraw', currency=currency, amount=amount,
                             address=address, paymentId=paymentId)