input: Write a function to generate a random string of the specified length using lowercase letters from the English alphabet. If the length is 0, return an empty string.
  assert random_string(6) in [''.join(random.choice(string.ascii_lowercase) for i in range(6)) for _ in range(100)]
  assert random_string(0) == ''
  assert len(random_string(4)) == 4
  assert all(c in string.ascii_lowercase for c in random_string(5))
output: import random
  import string
  
  def random_string(length):
      if length == 0:
          return ''
      return ''.join(random.choice(string.ascii_lowercase) for _ in range(length))