input: from typing import List
  
  def random_string(letters: List[str], length: int) -> str:
      """Generate a random string of the given length using the provided list of letters.
      >>> random_string(['a', 'b', 'c', 'd', 'e', 'f'], 6)
      'abcdef' # Note: This is just a placeholder, actual output will be random.
      """
output:     import random
      return ''.join(random.choices(letters, k=length))