input: 
  from typing import List
  
  
  def extract_words(words: str, letter: str) -> List[str]:
      """Extract all the words starting with a specific letter from a given string.
      >>> extract_words('This is a sample sentence to test the program', 's')
      ['sample', 'sentence', 'test', 'the', 'program']
      >>> extract_words('Running and jumping are fun activities', 'a')
      ['are', 'activities']
      """
      words_list = [w for w in words.split() if w.startswith(letter)]
      return words_list
  
output:     words_list = [w for w in words.split() if w.startswith(letter)]
      return words_list