code: def correct_word(word_string):
      '''
      Finds all valid one and two letter corrections for word_string, returning the word
      with the highest relative probability as type str.
      '''
      if word_string is None:
          return ""
      elif isinstance(word_string, str):
          return max(find_candidates(word_string), key=find_word_prob)
      else:
          raise InputError("string or none type variable not passed as argument to correct_word"f correct_word(word_string):
      '''
      Finds all valid one and two letter corrections for word_string, returning the word
      with the highest relative probability as type str.
      '''
      if word_string is None:
          return ""
      elif isinstance(word_string, str):
          return max(find_candidates(word_string), key=find_word_prob)
      else:
          raise InputError("string or none type variable not passed as argument to correct_word")
docs: Finds all valid one and two letter corrections for word_string, returning the word
      with the highest relative probability as type str.