code: def is_biallelic_01(self, min_mac=None):
          
          loc = self.is_biallelic() & (self.max_allele() == 1)
          if min_mac is not None:
              # noinspection PyAugmentAssignment
              loc = loc & (self.values[:, :2].min(axis=1) >= min_mac)
          return loc
docs: Find variants biallelic for the reference (0) and first alternate
          (1) allele.
  
          Parameters
          ----------
          min_mac : int, optional
              Minimum minor allele count.
  
          Returns
          -------
          out : ndarray, bool, shape (n_variants,)
              Boolean array where elements are True if variant matches the
              condition.