input: Write a function to generate a machine learning model using scikit-learn for classifying digits in the MNIST dataset. The function should load the dataset, split it into features and labels, reshape the data, and train a Logistic Regression classifier on the data.
  assert generate_mnist_model(fetch_openml('mnist_784'))==None
output: def generate_mnist_model(mnist_data):
      X, y = mnist_data.data, mnist_data.target
      X = X.reshape(X.shape[0], -1)
      model = LogisticRegression(max_iter=200)
      model.fit(X, y)