code: def true_fun(X):
      return np.cos(1.5 * np.pi * X)
  
imports: import matplotlib.pyplot
  import numpy
  from sklearn.linear_model import LinearRegression
  from sklearn.model_selection import cross_val_score
  from sklearn.pipeline import Pipeline
  from sklearn.preprocessing import PolynomialFeatures
label_desc: Use image node_id 1 for calling a global function with example usage: true_fun(X) and returns: np