Step 2: Backend Callbacks

[thanos]

Step 2: Backend Callbacks

Modify lib/ex_data_sketch/backend.ex

• Add 5 callbacks:

  @callback ull_new(opts()) :: state_bin()
  @callback ull_update(state_bin(), hash64(), opts()) :: state_bin()
  @callback ull_update_many(state_bin(), [hash64()], opts()) :: state_bin()
  @callback ull_merge(state_bin(), state_bin(), opts()) :: state_bin()
  @callback ull_estimate(state_bin(), opts()) :: float()