code: def join(self, words):
          
          chars = list(u"".join(words))
          start = True
  
          for i in xrange(len(chars)):
              char = chars[i]
              if char.isalpha():
                  if start:
                      chars[i] = char.upper()
                  else:
                      chars[i] = char.lower()
  
                  start = False
              else:
                  if i > 2 and chars[i - 1] in ".?!" and char.isspace():
                      start = True
  
          return u"".join(chars)
docs: Capitalize the first alpha character in the reply and the
          first alpha character that follows one of [.?!] and a
          space.