Charges for a reserved payment.

def settle(self, reserveTransactionId, transactionAmount=None):
        """
        Charges for a reserved payment.
        """
        params = {}
        params['ReserveTransactionId'] = reserveTransactionId
        if(transactionAmount != None):
            params['TransactionAmount'] = transactionAmount
        
        response = self.make_request("Settle", params)
        body = response.read()
        if(response.status == 200):
            rs = ResultSet()
            h = handler.XmlHandler(rs, self)
            xml.sax.parseString(body, h)
            return rs
        else:
            raise FPSResponseError(response.status, response.reason, body)