docs: def _mm_pairwise(n_items, data, params):
      """Inner loop of MM algorithm for pairwise data."""
      weights = exp_transform(params)
      wins = np.zeros(n_items, dtype=float)
      denoms = np.zeros(n_items, dtype=float)
      for winner, loser in data:
          wins[winner] += 1.0
          val = 1.0 / (weights[winner] + weights[loser])
          denoms[winner] += val
          denoms[loser] += val
      return wins, denoms