title: Error iterating through a Pandas series
body: <p>When I get the first and second elements of this series, it works OK, but from element 3 onwards, giving an error when I try to fetch.</p>
  
  <pre><code>type(X_test_raw)
  Out[51]: pandas.core.series.Series
  
  len(X_test_raw)
  Out[52]: 1393
  
  X_test_raw[0]
  Out[45]: 'Go until jurong point, crazy.. Available only in bugis n great world la e buffet... Cine there got amore wat...'
  
  X_test_raw[1]
  Out[46]: 'Ok lar... Joking wif u oni...'
  
  X_test_raw[2]
  </code></pre>
  
  <blockquote>
    <p>KeyError: 2</p>
  </blockquote>