code: def test_onehot_feature(self, params, titanic_data):
      onehot_feature_info = self.get_feature_info(
          titanic_data, **params
      )
      assert onehot_feature_info.type == "onehot"
  
      df, count_df, summary_df = onehot_feature_info.prepare(
          titanic_data
      )
      self.check_prepare_results(df, count_df, summary_df)
      assert np.array_equal(
          onehot_feature_info.grids, onehot_feature_info.col_name
      )
      assert onehot_feature_info.percentiles is None
      assert onehot_feature_info.num_bins == len(
          onehot_feature_info.col_name
      )
  
imports: import pandas
  import numpy
  import pytest
  from pdpbox.utils import FeatureInfo, _to_rgba, _check_col, _check_dataset, _make_list, _check_model, _check_classes, _check_memory_limit, _check_frac_to_plot, _calc_n_jobs, _get_string, _expand_params_for_interact, _calc_preds, _check_cluster_params, _check_plot_engine, _check_pdp_interact_plot_type
label_desc: Use image node_id 11 for calling the TestFeatureInfo obj's underlying member method code with example usage: obj.test_onehot_feature(params, titanic_data) without return types