input: Write a python function to make negative snippets of data for training using the `makeNegativeSnippets` function.
  assert len(makeNegativeSnippets({"magnetometer": [[1,2,3], [4,5,6], [7,8,9]], "labels": [], "filename": "test.json"}, 2)) == 2
  assert len(makeNegativeSnippets({"magnetometer": [[1,2,3], [4,5,6], [7,8,9]], "labels": [], "filename": "test.json"}, 1)) == 1
output: def makeNegativeSnippets(data, num_snippets):
      import random
      magnetometer_data = data["magnetometer"]
      snippet_length = len(magnetometer_data[0])
      snippets = []
  
      while len(snippets) < num_snippets:
          start_index = random.randint(0, len(magnetometer_data) - 1)
          snippet = magnetometer_data[start_index]
          snippets.append(snippet)
  
      return snippets