input: Write a Python function to add, edit, and delete key-value pairs in a dictionary and save the dictionary to a file using pickle.
  assert 'test_key' not in data
  add(data)
  assert data['test_key'] == 'test_value'
  edit(data)
  assert data['test_key'] == 'new_test_value'
  delete(data)
  assert 'test_key' not in data
output: import pickle
  
  def add(data):
      data['test_key'] = 'test_value'
      with open('data.pkl', 'wb') as f:
          pickle.dump(data, f)
  
  def edit(data):
      data['test_key'] = 'new_test_value'
      with open('data.pkl', 'wb') as f:
          pickle.dump(data, f)
  
  def delete(data):
      if 'test_key' in data:
          del data['test_key']
      with open('data.pkl', 'wb') as f:
          pickle.dump(data, f)