@spec chain([Celery.Canvas.Signature.t()], keyword()) ::
  {:ok, Celery.Result.t()} | {:error, term()}

Executes a sequential chain of %Celery.Canvas.Signature{} tasks.

In Celery Protocol v2, the first task in the chain is published with the remaining tasks stored in its chain embed list (in reverse order, as Python Celery pops from the end of request.chain!). Returns {:ok, last_task_result} with parent links pointing up the chain.

@spec chord([Celery.Canvas.Signature.t()], Celery.Canvas.Signature.t(), keyword()) ::
  {:ok, Celery.Result.t()} | {:error, term()}

Dispatches a chord (a parallel header of %Celery.Canvas.Signature{} tasks followed by a body callback %Celery.Canvas.Signature{} that receives the list of header results). Returns {:ok, callback_result}.

@spec group([Celery.Canvas.Signature.t()], keyword()) ::
  {:ok, Celery.Result.GroupResult.t()} | {:error, term()}

Dispatches a parallel group of %Celery.Canvas.Signature{} tasks and returns {:ok, %Celery.Result.GroupResult{}}.

@spec s(String.t() | map() | Celery.Canvas.Signature.t(), keyword()) ::
  Celery.Canvas.Signature.t()

Creates a %Celery.Canvas.Signature{} (s/2).

@spec si(String.t(), keyword()) :: Celery.Canvas.Signature.t()

Creates an immutable %Celery.Canvas.Signature{} (si/2).