input: Write a function to delete a given key from a dictionary. If the key does not exist in the dictionary, the dictionary should remain unchanged. The function should modify the dictionary in place and not return anything.
  
  def delete_key(dic, k):
    if k in dic:
      del dic[k]
  
  assert delete_key({'foo': 1, 'bar': 2, 'baz': 3}, 'baz')==None
  assert delete_key({'foo': 1, 'bar': 2}, 'baz')==None
  assert delete_key({}, 'baz')==None
  assert delete_key({'foo': 1, 'bar': 2, 'baz': 3}, 'foo')==None
output: def delete_key(dic, k):
    if k in dic:
      del dic[k]