code: def max_allele(self):
          
  
          out = np.empty(self.shape[0], dtype='i1')
          out.fill(-1)
          for i in range(self.shape[1]):
              d = self.values[:, i] > 0
              out[d] = i
          return out
docs: Return the highest allele index for each variant.
  
          Returns
          -------
          n : ndarray, int, shape (n_variants,)
              Allele index array.
  
          Examples
          --------
  
          >>> import allel
          >>> g = allel.GenotypeArray([[[0, 0], [0, 1]],
          ...                          [[0, 2], [1, 1]],
          ...                          [[2, 2], [-1, -1]]])
          >>> ac = g.count_alleles()
          >>> ac.max_allele()
          array([1, 2, 2], dtype=int8)