input: Write a python function to convert a JSON string into a dictionary.
  assert json_to_dict('{"name": "John", "age": 30, "city": "New York"}') == {"name": "John", "age": 30, "city": "New York"}
  assert json_to_dict('{"a": 1, "b": 2}') == {"a": 1, "b": 2}
  assert json_to_dict('{"key": "value", "number": 123}') == {"key": "value", "number": 123}
output: import json
  
  def json_to_dict(json_string):
      return json.loads(json_string)