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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 is_called(self):
 """Find non-missing genotype calls. Returns ------- out : ndarray, bool, shape (n_variants, n_samples) Array where elements are True if the genotype call matches the condition. Examples -------- array([[ True, True], [ True, True], [ True, False]]) <GenotypeVector shape=(3, 2) dtype=int64> 0/1 1/1 ./. array([ True, True, False]) """


        out = np.all(self.values >= 0, axis=-1)

        # handle mask
        if self.mask is not None:
            out &= ~self.mask

        return out