input: def extract_words(text: str, letter: str) -> List[str]:
      """
      Extracts all the words starting with a specific letter from a given text.
  
      >>> extract_words('This is a sample sentence to test the program', 's')
      ['sample', 'sentence', 'to', 'test']
      """
      words_list = []
      for w in text.split():
          if w[0].lower() == letter.lower():
              words_list.append(w)
      return words_list
output:     words_list = []
      for w in text.split():
          if w[0].lower() == letter.lower():
              words_list.append(w)
      return words_list