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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 create_refund(self, data=None, **params):
 """Create a refund for the order. When no data arg is given, a refund for all order lines is assumed."""

        if data is None:
            data = {'lines': []}
        refund = OrderRefunds(self.client).on(self).create(data, **params)
        return refund