title: How to import Airflow's PostgresOperator
body: <p>I'm trying to import the <code>PostgresOperator</code> from the airflow package:</p>
  <pre><code>from airflow.providers.postgres.operators.postgres import PostgresOperator
  </code></pre>
  <p>But I'm getting the following error: <code>Cannot find reference 'postgres' in imported module airflow.providers</code>.</p>