NameError in ipython-input with generate_X_grid

Question

    import pandas as pd
    from pygam import LogisticGAM
    from sklearn.datasets import load_breast_cancer

    #load the breast cancer data set
    data = load_breast_cancer()
    # keep first 6 features only
    df = pd.DataFrame(data.data, columns=data.feature_names) [['mean radius', 'mean texture', 'mean perimeter', 'mean area', 'mean smoothness', 'mean compactness']]
    target_df = pd.Series(data.target)
    df.describe()
    X = df[['mean radius', 'mean texture', 'mean perimeter', 'mean area', 'mean smoothness', 'mean compactness']]
    #Fit a model with the default parameters
    gam = LogisticGAM().fit(X,y)
    gam.accuracy(X,y)


    XX = generate_X_grid(gam)

Error:

NameError
<ipython-input-17-xxx 
 ---> 1 XX = generate_X_grid(gam)
NameError: name 'generate_X_grid' is not defined