input: Write a python function to load a machine learning model from a pickle file and return it.
  assert load_model('model1').__class__.__name__ == 'SomeModelClass'
  assert load_model('model2').__class__.__name__ == 'AnotherModelClass'
  assert load_model('non_existent_model') is None
output: def load_model(file_path):
      import pickle
      try:
          with open(file_path, 'rb') as f:
              model = pickle.load(f)
          return model
      except (FileNotFoundError, pickle.UnpicklingError):
          return None