def intersect(L1, L2):
   """Assumes: L1 and L2 are lists
      Returns a list without duplicates that is the intersection of
      L1 and L2"""
   #Build a list containing common elements
   tmp = []
   for e1 in L1:
      for e2 in L2:
         if e1 == e2:
            tmp.append(e1)
            break
   #Build a list without duplicates
   result = []
   for e in tmp:
      if e not in result:
         result.append(e)
   return result