title: AttributeError: 'str' object has no attribute 'parameters' due to new version of sklearn
body: <p>I am doing topic modeling using sklearn. While trying to get the log-likelihood from Grid Search output, I am getting the below error: </p>
  
  <blockquote>
    <p>AttributeError: 'str' object has no attribute 'parameters'</p>
  </blockquote>
  
  <p>I think I understand the issue which is: 'parameters' is used in the older version and I am using the new version (0.22) of sklearn and that is giving error. I also search for the term which is used in the new version but couldn't find it. Below is the code:</p>
  
  <pre><code># Get Log Likelyhoods from Grid Search Output
  n_components = [10, 15, 20, 25, 30]
  log_likelyhoods_5 = [round(gscore.mean_validation_score) for gscore in model.cv_results_ if gscore.parameters['learning_decay']==0.5]
  log_likelyhoods_7 = [round(gscore.mean_validation_score) for gscore in model.cv_results_ if gscore.parameters['learning_decay']==0.7]
  log_likelyhoods_9 = [round(gscore.mean_validation_score) for gscore in model.cv_results_ if gscore.parameters['learning_decay']==0.9]
  
  # Show graph
  plt.figure(figsize=(12, 8))
  plt.plot(n_components, log_likelyhoods_5, label='0.5')
  plt.plot(n_components, log_likelyhoods_7, label='0.7')
  plt.plot(n_components, log_likelyhoods_9, label='0.9')
  plt.title("Choosing Optimal LDA Model")
  plt.xlabel("Num Topics")
  plt.ylabel("Log Likelyhood Scores")
  plt.legend(title='Learning decay', loc='best')
  plt.show()
  </code></pre>
  
  <p>Thanks in advance!</p>