code: def list_order_by(l,firstItems):
      
      l=list(l)
      for item in firstItems[::-1]: #backwards
          if item in l:
              l.remove(item)
              l.insert(0,item)
      return l
docs: given a list and a list of items to be first, return the list in the
      same order except that it begins with each of the first items.