title: "Import could not be resolved" reported by Pyright
body: <p><a href="https://i.stack.imgur.com/6wfHa.png" rel="noreferrer"><img src="https://i.stack.imgur.com/6wfHa.png" alt="enter image description here"></a></p>
  
  <p>I've just started using <a href="https://marketplace.visualstudio.com/items?itemName=ms-pyright.pyright" rel="noreferrer">Pyright</a>. Running it on files that run perfectly well I get plenty of errors.</p>
  
  <p><a href="https://stackoverflow.com/questions/59108805/fixing-import-module-could-not-be-resolved-in-pyright">This question</a> is similar, but refers to one's own modules.</p>
  
  <p>For example <code>Import "numpy" could not be resolved</code>. What does it mean, and how do I resolve it?</p>