input: Write a python function to extract the value of the "name" key from a JSON string.
  assert extract_name('{"name": "John", "age": 28, "location": "New York"}') == "John"
  assert extract_name('{"name": "Alice", "age": 30, "location": "Los Angeles"}') == "Alice"
  assert extract_name('{"name": "Bob", "age": 22, "location": "Chicago"}') == "Bob"
output: import json
  
  def extract_name(json_str):
      data = json.loads(json_str)
      return data["name"]