input: Write a python function to convert a Python dictionary to a JSON string using the json module.
  assert dict_to_json({"name": "John", "age": 30, "location": "Greece"}) == '{"name": "John", "age": 30, "location": "Greece"}'
  assert dict_to_json({"title": "Inception", "year": 2010, "genre": "Sci-Fi"}) == '{"title": "Inception", "year": 2010, "genre": "Sci-Fi"}'
  assert dict_to_json({"company": "OpenAI", "product": "GPT-3", "launch_year": 2020}) == '{"company": "OpenAI", "product": "GPT-3", "launch_year": 2020}'
output: import json
  
  def dict_to_json(data):
      return json.dumps(data)