code: def chi_square(X, y):
      """
      This function implements the chi-square feature selection (existing method for classification in scikit-learn)
  
      Input
      -----
      X: {numpy array}, shape (n_samples, n_features)
          input data
      y: {numpy array},shape (n_samples,)
          input class labels
  
      Output
      ------
      F: {numpy array}, shape (n_features,)
          chi-square score for each feature
      """
      F, pval = chi2(X, y)
      return F
  
label_desc: Use image node_id 1 for calling a global function with example usage: chi_square(X, y) and returns: F