title: In airflow, is there a good way to call another dag's task?
body: <p>I've got dag_prime and dag_tertiary.  </p>
  
  <ul>
  <li><code>dag_prime</code>: Scans through a directory and intends to call dag_tertiary
  on each one.  Currently a PythonOperator.  </li>
  <li><code>dag_tertiary</code>: Scans through the directory passed to it and does (possibly time-intensive) calculations on the contents thereof.</li>
  </ul>
  
  <p>I can call the secondary one from a system call from the python operator, but i feel like there's got to be a better way.  I'd also like to consider queuing the dag_tertiary calls, if there's a simple way to do that.  Is there a better way than using system calls?  </p>
  
  <p>Thanks!</p>