In the previous example, we saw how to call a Lambda function using a Python-based step function.
Step Functions also has a feature called activities: these are similar to tasks, but with a different invocation mechanism. (At the workflow level they look the same as tasks, but the activity implementation pulls requests from a queue instead of getting requests over an API.)
Calling a Step Functions Activity looks similar to calling a function: use cohesion.activity to send a task to the activity.
Just as in the Lambda example, Cohesion uses your configured region and account ID to generate the ARN of the Activity.
Building the activity itself is outside the scope of cohesion; most people who use activities already have some sort of service they want to orchestrate. Activities are a useful intermediate step between a monolith and a fully serverless system.