input: Write a function to generate a random string of length 6. Use the string.ascii_lowercase for the characters and random.choice to pick the characters. Return the generated string.
  
  assert random_string(6)==random_string(6)
  assert len(random_string(6))==6
  assert isinstance(random_string(6), str)
  assert random_string(6) in ''.join(random.choice(string.ascii_lowercase) for i in range(6))
output: import string
  import random
  
  def random_string(length):
      return ''.join(random.choice(string.ascii_lowercase) for i in range(length))