input: Write a function to generate a random string of a specified length. The function should accept an integer as input and return a string of that length composed of lowercase English letters.
  
  def random_string(length):
      letters = string.ascii_lowercase
      return ''.join(random.choice(letters) for i in range(length))
  
  assert random_string(6) in [''.join(p) for p in itertools.product(string.ascii_lowercase, repeat=6)]
  assert len(random_string(6)) == 6
  assert random_string(0) == ''
  assert random_string(10).islower()
  assert all(c in string.ascii_lowercase for c in random_string(8))
output: def random_string(length):
      letters = string.ascii_lowercase
      return ''.join(random.choice(letters) for i in range(length))