input: Write a Python function to retrieve the value associated with a given key from a dictionary.
  assert get_value(user_info, 'name') == 'John Smith'
  assert get_value(user_info, 'age') == 32
  assert get_value(user_info, 'location') == 'USA'
  assert get_value(user_info, 'email') is None
output: def get_value(dictionary, key):
      return dictionary.get(key)