Task signature methods

When chaining Celery tasks, choose the correct signature method:

• Use .s() when a task needs the output from the previous task in the chain
• Use .si() (immutable signature) when a task doesn’t need any output from the previous task

Incorrect signature methods can cause task failures or unexpected data flow between tasks.

# Example of proper signature method usage:
chain(
    initial_task.si(param1=value1),  # First task or doesn't need previous output
    process_results.s(),  # Needs output from initial_task
    save_to_database.si(param2=value2)  # Independent task with static parameters
)