title: Pandas slicing FutureWarning with 0.21.0
body: <p>I'm trying to select a subset of a subset of a dataframe, selecting only some columns, and filtering on the rows.</p>
  
  <pre><code>df.loc[df.a.isin(['Apple', 'Pear', 'Mango']), ['a', 'b', 'f', 'g']]
  </code></pre>
  
  <p>However, I'm getting the error:</p>
  
  <pre><code>Passing list-likes to .loc or [] with any missing label will raise
  KeyError in the future, you can use .reindex() as an alternative.
  </code></pre>
  
  <p>What 's the correct way to slice and filter now?</p>