code: def sumdiffsquared(x, y):
      
      sds = 0
      for i in range(len(x)):
          sds = sds + (x[i] - y[i]) ** 2
      return sds
docs: Takes pairwise differences of the values in lists x and y, squares
  these differences, and returns the sum of these squares.
  
  Usage:   lsumdiffsquared(x,y)
  Returns: sum[(x[i]-y[i])**2]