title: save cv_results_['params'] from grid search as csv
body: <p>I would like to save my scores and parameters used in my grid search as a csv file. The problem is, that the parameters are all saved in the same column. Here is an example:</p>
  
  <pre><code>param_grid=dict(batch_size=batch_size, epochs=epochs)
  
  grid = GridSearchCV(estimator=model, param_grid=param_grid, n_jobs=-1, cv=3)
  grid_result = grid.fit(x_train, y_train, validation_data=(x_test, y_test), callbacks=[es])
  
  means = grid_result.cv_results_['mean_test_score']
  stds = grid_result.cv_results_['std_test_score']
  param = grid_result.cv_results_['params']
  
  exportfile='/Users/test.csv'
  with open(exportfile, 'w', newline='') as file:
      writer = csv.writer(file)
      for mean, stdev, param in zip(means, stds, params):
          writer.writerow([mean, stdev, param])
  </code></pre>
  
  <p>The output of the param is like this:</p>
  
  <p>{'batch_size': 40, 'epochs': 1000}</p>
  
  <p>but I want to reduce it to:</p>
  
  <p>40, 1000</p>