title: PyMongo $in + $regex
body: <p>How can I combine $regex with $in in PyMongo?</p>
  
  <p>I want to search for either <code>/*.heavy.*/</code> or <code>/*.metal.*/</code>.</p>
  
  <p>I tried in python without success:</p>
  
  <pre><code>db.col.find({'music_description' : { '$in' : [ {'$regex':'/*.heavy.*/'} ]} })
  </code></pre>
  
  <p>The equivalent in Mongo shell is:</p>
  
  <pre><code>db.inventory.find( { music_description: { $in: [ /heavy/, /metal/ ] } } )
  </code></pre>