input: Write a python function to train a decision tree classifier using the 'Skewness' feature and the 'Target' column from a given DataFrame.
  assert train_decision_tree(df).classes_.tolist() == [0, 1]
  assert hasattr(train_decision_tree(df), 'tree_')
  assert train_decision_tree(df).random_state == 0
output: def train_decision_tree(df):
      from sklearn.tree import DecisionTreeClassifier
  
      X = df[['Skewness']]
      y = df['Target']
  
      clf = DecisionTreeClassifier(random_state=0)
      clf.fit(X, y)
  
      return clf