new_contents: class Solution(object):
      def findWords(self, words):
          """
          :type words: List[str]
          :rtype: List[str]
          """
          ret = []
          row1 = set('qwertyuiop')
          row2 = set('asdfghjkl')
          row3 = set('zxcvbnm')
          
          for i in words:
              t = set(i.lower())
              if row1 & t == t:
                  ret.append(i)
              if row2 & t == t:
                  ret.append(i)
              if row3 & t == t:
                  ret.append(i)
          return ret
  
subject: Create 500-Keyboard-Row.py