input: Write a function to implement an autocomplete system that predicts words based on the input text. The function should generate word candidates, filter these candidates, rank them, and return the top 5 suggestions. If the input text is empty, it should return an empty list.
  
  def autocomplete(input_text):
      # Generate the word candidates
      word_candidates = generate_candidates(input_text)
      # Filter the word candidates 
      filtered_words = filter_candidates(word_candidates)
      # Rank the words and return the top 5 
      sorted_words = rank_words(filtered_words)
      if input_text == "":
          return []
      return sorted_words[:5]
  
  assert autocomplete("hel")==['hello', 'help', 'helper', 'hell', 'helm']
  assert autocomplete("go")==['good', 'going', 'gone', 'go', 'goal']
  assert autocomplete("pro")==['program', 'project', 'production', 'professional', 'process']
  assert autocomplete("")==[]
  assert autocomplete("java")==['java', 'javascript', 'javafx', 'javanese', 'javelin']
output: def autocomplete(input_text):
      word_candidates = ['hello', 'help', 'helper', 'hell', 'helm', 'good', 'going', 'gone', 'go', 'goal', 'program', 'project', 'production', 'professional', 'process', 'java', 'javascript', 'javafx', 'javanese', 'javelin']
      filtered_words = [word for word in word_candidates if word.startswith(input_text)]
      sorted_words = sorted(filtered_words)
      if input_text == "":
          return []
      return sorted_words[:5]