input: Write a function to delete a given key from a dictionary. If the key exists in the dictionary, it should be removed. If the key does not exist, the dictionary should remain unchanged.
  def delete_key(dic, k):
    if k in dic:
      del dic[k]
  
  assert delete_key({'foo': 1, 'bar': 2, 'baz': 3}, 'baz') == {'foo': 1, 'bar': 2}
  assert delete_key({'foo': 1, 'bar': 2}, 'baz') == {'foo': 1, 'bar': 2}
  assert delete_key({}, 'baz') == {}
output: def delete_key(dic, k):
    if k in dic:
      del dic[k]