input: from typing import List
  
  def reverse_words(sentence: str) -> str:
      """
      Reverse the order of words in a sentence while maintaining the order of characters in each word.
      
      >>> reverse_words('This is a sentence.')
      'sentence. a is This'
      >>> reverse_words('Python is easy to learn.')
      'learn. to easy is Python'
      """
      words = sentence.split()
      reversed_words = words[::-1]
      return ' '.join(reversed_words)
output:     words = sentence.split()
      reversed_words = words[::-1]
      return ' '.join(reversed_words)