input: from typing import List, Dict
  
  def extract_words(word: 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', 'to', 'test', 'the', 'program']
      """
      words_list = [w for w in word.split() if w[0] == letter]
      return words_list
output:     words_list = [w for w in word.split() if w[0] == letter]
      return words_list