code: def _choose_split_points(cls, sorted_keys, shard_count):
      
      assert len(sorted_keys) >= shard_count
      index_stride = len(sorted_keys) / float(shard_count)
      return [sorted_keys[int(round(index_stride * i))]
              for i in range(1, shard_count)]
docs: Returns the best split points given a random set of datastore.Keys.