code: def _invert(h):
          "Cheap function to invert a hash."
          i = {}
          for k,v in h.items():
              i[v] = k
          return f _invert(h):
          "Cheap function to invert a hash."
          i = {}
          for k,v in h.items():
              i[v] = k
          return i
docs: Cheap function to invert a hash.