title: xgboost model getfscore:'str' object is not callable
body: <pre><code>feat_imp = pd.Series(xgbPara.booster().get_fscore()).sort_values(ascending=False) 
  
  TypeError: 'str' object is not callable
  </code></pre>
  
  <p>I can run it in pycharm, but when I run it in pyspark, there is a Type Error.</p>
  
  <p>could anyone tell me why? Thanks！</p>