input: Write a function to fit KMeans and GaussianMixture models and return the GaussianMixture model.
  assert isinstance(fit_models(X, n_clusters), GaussianMixture)
  assert fit_models([[1, 2], [1, 4], [1, 0], [10, 2], [10, 4], [10, 0]], 2).n_components == 2
output: def fit_models(X, n_clusters):
      from sklearn.cluster import KMeans
      from sklearn.mixture import GaussianMixture
      
      # Fit KMeans model
      kmeans = KMeans(n_clusters=n_clusters)
      kmeans.fit(X)
      
      # Fit Gaussian Mixture Model
      gmm = GaussianMixture(n_components=n_clusters)
      gmm.fit(X)
      
      return gmm