input: Write a python function to find a value from a dictionary given a key.
  assert find_value({'name': 'John', 'age': 26, 'salary': 5000}, 'name') == 'John'
  assert find_value({'name': 'John', 'age': 26, 'salary': 5000}, 'age') == 26
  assert find_value({'name': 'John', 'age': 26, 'salary': 5000}, 'salary') == 5000
  assert find_value({'name': 'John', 'age': 26, 'salary': 5000}, 'address') == None
output: def find_value(dictionary, key):
      return dictionary.get(key, None)