input: Write a python function to generate song lyrics with given number of lines and words per line.
  assert len(generate_lyrics(8, 4).split('\n')) == 9  # 8 lines + 1 for the final string
  assert generate_lyrics(5, 3).count('.') == 5  # 5 lines ending with '.'
  assert len(generate_lyrics(3, 2).split('\n')) == 4  # 3 lines + 1 for the final string
output: def generate_lyrics(num_lines, words_per_line):
      import random
      import string
      
      def generate_word(length):
          return ''.join(random.choices(string.ascii_lowercase, k=length))
      
      lyrics = []
      for _ in range(num_lines):
          line = ' '.join(generate_word(random.randint(3, 7)) for _ in range(words_per_line)) + '.'
          lyrics.append(line)
      
      return '\n'.join(lyrics) + '\n'