input: Write a function to generate a poem based on the input list.
  assert generate_poem(['roses', 'are', 'red']) == ['', 'roses ', 'roses are ']
  assert generate_poem(['sky', 'is', 'blue']) == ['', 'sky ', 'sky is ']
  assert generate_poem(['hello', 'world']) == ['', 'hello ']
output: def generate_poem(words):
      poem = ['']
      current_line = ''
      for word in words:
          current_line += word + ' '
          poem.append(current_line)
      return poem