# Buggy code
def __init__(self, obj, *args, **kwargs):
    parent = kwargs.pop("parent", None)
    groupby = kwargs.pop("groupby", None)
    if parent is None:
        parent = obj

    # initialize our GroupByMixin object with
    # the resampler attributes
    for attr in self._attributes:
        setattr(self, attr, kwargs.get(attr, getattr(parent, attr)))

    super(_GroupByMixin, self).__init__(None)
    self._groupby = groupby
    self._groupby.mutated = True
    self._groupby.grouper.mutated = True
    self.groupby = parent.groupby


# Traceback (KeyError)
/usr/local/bin/ipython:1: FutureWarning: .resample() is now a deferred operation
use .resample(...).mean() instead of .resample(...)
#!/usr/local/opt/python/bin/python2.7
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-30-5714547cf98c> in <module>()
----> 1 resampler['buyer'].count()

/usr/local/lib/python2.7/site-packages/pandas/tseries/resample.pyc in __getitem__(self, key)
179             # compat for deprecated
180             if isinstance(self.obj, com.ABCSeries):
--> 181                 return self._deprecated()[key]
182
183             raise

/usr/local/lib/python2.7/site-packages/pandas/core/frame.pyc in __getitem__(self, key)
1995             return self._getitem_multilevel(key)
1996         else:
-> 1997             return self._getitem_column(key)
1998
1999     def _getitem_column(self, key):

/usr/local/lib/python2.7/site-packages/pandas/core/frame.pyc in _getitem_column(self, key)
2002         # get column
2003         if self.columns.is_unique:
-> 2004             return self._get_item_cache(key)
2005
2006         # duplicate columns &amp; possible reduce dimensionality

/usr/local/lib/python2.7/site-packages/pandas/core/generic.pyc in _get_item_cache(self, item)
1348         res = cache.get(item)
1349         if res is None:
-> 1350             values = self._data.get(item)
1351             res = self._box_item_values(item, values)
1352             cache[item] = res

/usr/local/lib/python2.7/site-packages/pandas/core/internals.pyc in get(self, item, fastpath)
3288
3289             if not isnull(item):
-> 3290                 loc = self.items.get_loc(item)
3291             else:
3292                 indexer = np.arange(len(self.items))[isnull(self.items)]

/usr/local/lib/python2.7/site-packages/pandas/indexes/base.pyc in get_loc(self, key, method, tolerance)
1945                 return self._engine.get_loc(key)
1946             except KeyError:
-> 1947                 return self._engine.get_loc(self._maybe_cast_indexer(key))
1948
1949         indexer = self.get_indexer([key], method=method, tolerance=tolerance)

pandas/index.pyx in pandas.index.IndexEngine.get_loc (pandas/index.c:4154)()

pandas/index.pyx in pandas.index.IndexEngine.get_loc (pandas/index.c:4018)()

pandas/hashtable.pyx in pandas.hashtable.PyObjectHashTable.get_item (pandas/hashtable.c:12368)()

pandas/hashtable.pyx in pandas.hashtable.PyObjectHashTable.get_item (pandas/hashtable.c:12322)()

KeyError: 'buyer'

# Fixed code
def __init__(self, obj, *args, **kwargs):
    parent = kwargs.pop("parent", None)
    groupby = kwargs.pop("groupby", None)
    if parent is None:
        parent = obj

    # initialize our GroupByMixin object with
    # the resampler attributes
    for attr in self._attributes:
        setattr(self, attr, kwargs.get(attr, getattr(parent, attr)))

    super(_GroupByMixin, self).__init__(None)
    self._groupby = groupby
    self._groupby.mutated = True
    self._groupby.grouper.mutated = True
    self.groupby = copy.copy(parent.groupby)