input: Write a function to implement an autocomplete system that predicts words based on the input text. The function should generate possible word candidates from the input text, filter them, rank them, and return the top 5 predictions. If the input text is empty, the function should return an empty list.
  def autocomplete(input_text):
      if not input_text:
          return []
      word_candidates = generate_candidates(input_text)
      filtered_words = filter_candidates(word_candidates)
      sorted_words = rank_words(filtered_words)
      return sorted_words[:5]
  assert autocomplete("hel") == ["hello", "help", "helmet", "hell", "helix"]
  assert autocomplete("run") == ["running", "runner", "runs", "runway", "rune"]
  assert autocomplete("pro") == ["product", "program", "project", "professional", "promote"]
  assert autocomplete("ca") == ["car", "cat", "case", "can", "cake"]
  assert autocomplete("") == []
output: def autocomplete(input_text):
      if not input_text:
          return []
      word_candidates = generate_candidates(input_text)
      filtered_words = filter_candidates(word_candidates)
      sorted_words = rank_words(filtered_words)
      return sorted_words[:5]