How does Airflow's BranchPythonOperator work?
问题 I'm struggling to understand how BranchPythonOperator in Airflow works. I know it's primarily used for branching, but am confused by the documentation as to what to pass into a task and what I need to pass/expect from the task upstream. Given the simple example in the documentation on this page what would the source code look like for the upstream task called run_this_first and the 2 downstream ones that are branched? How exactly does Airflow know to run branch_a instead of branch_b ? Where