input: Write a function to generate a random string of a specified length using lowercase letters. The function should take an integer argument representing the length of the string and return the generated string.
  import random
  import string
  
  def random_string(length):
      letters = string.ascii_lowercase
      return ''.join(random.choice(letters) for i in range(length))
  
  assert random_string(6) != random_string(6)  # Checking if successive calls produce different results
  assert len(random_string(6)) == 6  # Checking if the length of the string is correct
  assert random_string(0) == ""  # Checking if length 0 returns an empty string
output: import random
  import string
  
  def random_string(length):
      letters = string.ascii_lowercase
      return ''.join(random.choice(letters) for i in range(length))