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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 fill_masked(self, value=-1, copy=True):
 """Fill masked genotype calls with a given value. Parameters value : int, optional The fill value. copy : bool, optional If False, modify the array in place. Returns ------- g : GenotypeArray Examples -------- array([[[-1, -1], [ 0, 1]], [[ 0, 1], [-1, -1]], [[ 0, 2], [-1, -1]]], dtype=int8) """


        if self.mask is None:
            raise ValueError('no mask is set')

        # apply the mask
        data = np.array(self.values, copy=copy)
        data[self.mask, ...] = value

        if copy:
            out = type(self)(data)  # wrap
            out.is_phased = self.is_phased
            # don't set mask because it has been filled in
        else:
            out = self
            out.mask = None  # reset mask

        return out