input: Write a python function to fetch and return the 'name' key from a given URL's JSON response.
  ```python
  import requests
  
  def fetch_user_name(url):
      userdata = requests.get(url).json()
      return userdata['name']
  
  # Test cases
  assert fetch_user_name('http://example.com/api/userdata') == 'ExpectedName1'
  assert fetch_user_name('http://example.com/api/userdata2') == 'ExpectedName2'
  assert fetch_user_name('http://example.com/api/userdata3') == 'ExpectedName3'
output: import requests
  
  def fetch_user_name(url):
      userdata = requests.get(url).json()
      return userdata['name']