input: Write a python function to extract temperature from a JSON string.
  assert extract_temperature('{"location": "Berlin", "weather": {"temperature": 17.6}}') == 17.6
  assert extract_temperature('{"location": "New York", "weather": {"temperature": 20.1}}') == 20.1
  assert extract_temperature('{"location": "Tokyo", "weather": {"temperature": 22.5}}') == 22.5
output: import json
  
  def extract_temperature(json_string):
      data = json.loads(json_string)
      return data['weather']['temperature']