input: Write a python function to convert a JSON object to a dictionary.
  assert json_to_dict('{"key1": "value1", "key2": "value2"}') == {"key1": "value1", "key2": "value2"}
  assert json_to_dict('{"a": 1, "b": 2, "c": 3}') == {"a": 1, "b": 2, "c": 3}
  assert json_to_dict('{"name": "John", "age": 30}') == {"name": "John", "age": 30}
output: import json
  
  def json_to_dict(json_str):
      return json.loads(json_str)