title: Filter Pandas dataframe with another series
body: <p>I have Pandas Series we'll call approved_fields which I'd like to use to filter a df by:</p>
  
  <pre><code>approved_field(['Field1','Field2','Field3')]
  
  df
      Field
  0   Field1
  1   Field4
  2   Field2
  3   Field5
  4   Field2
  </code></pre>
  
  <p>After applying the approved_field filter, the resulting df should look like:</p>
  
  <pre><code>    Field
  0   Field1
  1   Field2
  2   Field2
  </code></pre>
  
  <p>Thanks!</p>