input: from typing import List
  
  def extract_words(word: str, letter: str) -> List[str]:
      """Extract all the words starting with a specific letter
      >>> extract_words('This is a sample sentence to test the program', 's')
      ['sentence', 'sample', 'to']
      >>> extract_words('Another example for testing purposes', 't')
      ['testing', 'the']
      """
      words_list = []
      for w in word.split():
          if w[0] == letter:
              words_list.append(w)
      return words_list
output:     words_list = []
      for w in word.split():
          if w[0] == letter:
              words_list.append(w)
      return words_list