input: Write a function to delete a given key from a dictionary.
  
  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({}, 'baz') == None
  assert delete_key({'foo': 1, 'bar': 2, 'baz': 3}, 'foo') == None
  assert delete_key({'foo': 1, 'bar': 2, 'baz': 3}, 'bar') == None
  
  print({'foo': 1, 'bar': 2, 'baz': 3} == {'foo': 1, 'bar': 2})
  print({'foo': 1, 'bar': 2, 'baz': 3} == {'foo': 1, 'bar': 2, 'baz': 3})
  print({} == {})
  print({'foo': 1, 'bar': 2, 'baz': 3} == {'foo': 1, 'bar': 2})
  print({'foo': 1, 'bar': 2, 'baz': 3} == {'foo': 1, 'baz': 3})
output: def delete_key(dic, k):
    if k in dic:
      del dic[k]