input: Write a function to delete a given key from a dictionary. If the key exists in the dictionary, it should be removed; otherwise, 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')==None
  assert delete_key({'foo': 1, 'bar': 2, 'baz': 3}, 'qux')==None
  assert delete_key({}, 'foo')==None
  assert delete_key({'foo': 1}, 'foo')==None
  assert delete_key({'foo': 1, 'bar': 2}, 'bar')==None
  
  # Dictionary after deleting the key
  assert {'foo': 1, 'bar': 2}=={'foo': 1, 'bar': 2}
  assert {'foo': 1, 'bar': 2, 'baz': 3}=={'foo': 1, 'bar': 2, 'baz': 3}
  assert {}=={}
  assert {}=={}
  assert {'foo': 1}=={'foo': 1}
output: def delete_key(dic, k):
    if k in dic:
      del dic[k]