code: def is_called(self):
          
  
          out = np.all(self.values >= 0, axis=-1)
  
          # handle mask
          if self.mask is not None:
              out &= ~self.mask
  
          return out
docs: 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
          --------
  
          >>> import allel
          >>> g = allel.GenotypeArray([[[0, 0], [0, 1]],
          ...                          [[0, 1], [1, 1]],
          ...                          [[0, 2], [-1, -1]]])
          >>> g.is_called()
          array([[ True,  True],
                 [ True,  True],
                 [ True, False]])
          >>> v = g[:, 1]
          >>> v
          <GenotypeVector shape=(3, 2) dtype=int64>
          0/1 1/1 ./.
          >>> v.is_called()
          array([ True,  True, False])