input: Write a function to delete a given key from a dictionary. If the key is not present in the dictionary, the dictionary should remain unchanged. The function should return the updated dictionary.
  
  def delete_key(dic, k):
    if k in dic:
      del dic[k]
    return dic
  
  assert delete_key({'foo': 1, 'bar': 2, 'baz': 3}, 'baz')=={'foo': 1, 'bar': 2}
  assert delete_key({'foo': 1, 'bar': 2, 'baz': 3}, 'qux')=={'foo': 1, 'bar': 2, 'baz': 3}
  assert delete_key({}, 'baz')=={}
output: def delete_key(dic, k):
    if k in dic:
      del dic[k]
    return dic