input: Write a function to delete a specified key from a given dictionary. If the key is present, the function should remove it from the dictionary. If the key is not present, the dictionary should remain unchanged. The function should return the modified 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({}, 'foo') == {}
output: def delete_key(dic, k):
      if k in dic:
          del dic[k]
      return dic