Error in solution in Pandas tutorial

[dimka11]

price_extremes = reviews.groupby('variety').price.agg([min, max])

TypeError                                 Traceback (most recent call last)
<ipython-input-81-1ee08b4f09ca> in <module>
      1 #q3.hint()
      2 q3.solution()
----> 3 price_extremes = reviews.groupby('variety').price.agg([min, max])

/opt/conda/lib/python3.6/site-packages/pandas/core/groupby/generic.py in aggregate(self, func_or_funcs, *args, **kwargs)
    849             # but not the class list / tuple itself.
    850             func_or_funcs = _maybe_mangle_lambdas(func_or_funcs)
--> 851             ret = self._aggregate_multiple_funcs(func_or_funcs, (_level or 0) + 1)
    852             if relabeling:
    853                 ret.columns = columns

/opt/conda/lib/python3.6/site-packages/pandas/core/groupby/generic.py in _aggregate_multiple_funcs(self, arg, _level)
    916         for name, func in arg:
    917             obj = self
--> 918             if name in results:
    919                 raise SpecificationError(
    920                     "Function names must be unique, found multiple named "

/opt/conda/lib/python3.6/site-packages/pandas/core/generic.py in __hash__(self)
   1884         raise TypeError(
   1885             "{0!r} objects are mutable, thus they cannot be"
-> 1886             " hashed".format(self.__class__.__name__)
   1887         )
   1888 

TypeError: 'Series' objects are mutable, thus they cannot be hashed

Exercise: Grouping and Sorting - point 3