input: Write a python function to train a Linear Regression model and predict the test set using given training and test data.
  assert len(train_and_predict(X_train, X_test, Y_train)) == len(Y_test)
output: def train_and_predict(X_train, X_test, Y_train):
      from sklearn.linear_model import LinearRegression
      model = LinearRegression()
      model.fit(X_train, Y_train)
      predictions = model.predict(X_test)
      return predictions