new_contents: class Solution:
      # @return a list of lists of integers
  
      def generate(self, numRows):
          if numRows <= 0:
              return []
          res = [[1]]
          for i in xrange(1, numRows):
              line = [1]
              for j in xrange(1, i+1):
                  if j == i:
                      line.append(1)
                      res.append(line)
                  else:
                      line.append(res[i-1][j-1]+res[i-1][j])
          return res
  
subject: add solution for Pascals Triangle