input: Write a python function to create a decision tree model using scikit-learn.
  assert isinstance(create_tree_model([[0, 0], [1, 1]], [0, 1]), tree.DecisionTreeClassifier)
  assert hasattr(create_tree_model([[0, 0], [1, 1]], [0, 1]), 'predict')
  assert create_tree_model([[0, 0], [1, 1]], [0, 1]).predict([[2, 2]]) is not None
output: def create_tree_model(X, y):
      from sklearn import tree
      clf = tree.DecisionTreeClassifier()
      clf = clf.fit(X, y)
      return clf