input: Write a function to delete a given key from a dictionary and return the modified dictionary. If the key is not found, the original dictionary should be returned unchanged. If the input dictionary is empty, return an empty 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