code: def random_string(**kwargs):
      
      n = kwargs.get('length', 10)
      pool = kwargs.get('pool') or string.digits + string.ascii_lowercase
      return ''.join(random.SystemRandom().choice(pool) for _ in range(n))
docs: By default generates a random string of 10 chars composed
      of digits and ascii lowercase letters. String length and pool can
      be override by using kwargs. Pool must be a list of strings