input: Write a python function to generate a random string of a given length using lowercase letters.
  assert len(randomString(10)) == 10
  assert len(randomString(5)) == 5
  assert len(randomString(15)) == 15
output: import string
  import random
  
  def randomString(length):
      return ''.join(random.choice(string.ascii_lowercase) for _ in range(length))