code: def popitem(self):
          
          try:
              value = next(iter(self))
              key = value[self._keycol]
          except StopIteration:
              raise KeyError
          del self[key]
          return key, value
docs: D.popitem() -> (k, v)
          
          Remove and return some (key, value) pair
          as a 2-tuple; but raise KeyError if D is empty.