input: Write a python function to convert a JSON string to a dictionary.
  assert json_to_dict('{"name": "GPT", "type": "AI"}') == {"name": "GPT", "type": "AI"}
  assert json_to_dict('{"age": 30, "language": "Python"}') == {"age": 30, "language": "Python"}
  assert json_to_dict('{}') == {}
output: import json
  
  def json_to_dict(json_string):
      return json.loads(json_string)