code: def _commonWordStart(self, words):
          
          if not words:
              return ''
  
          length = 0
          firstWord = words[0]
          otherWords = words[1:]
          for index, char in enumerate(firstWord):
              if not all([word[index] == char for word in otherWords]):
                  break
              length = index + 1
  
          return firstWord[:length]
docs: Get common start of all words.
          i.e. for ['blablaxxx', 'blablayyy', 'blazzz'] common start is 'bla'