Parameters
        ----------
        method : string {'backfill', 'bfill', 'pad', 'ffill'}
            method for upsampling
        limit : int, default None
            Maximum size gap to fill when reindexing
        fill_value : scalar, default None
            Value to use for missing values

        See Also
        --------
        .fillna

def _upsample(self, method, limit=None, fill_value=None):
        """
        Parameters
        ----------
        method : string {'backfill', 'bfill', 'pad', 'ffill'}
            method for upsampling
        limit : int, default None
            Maximum size gap to fill when reindexing
        fill_value : scalar, default None
            Value to use for missing values

        See Also
        --------
        .fillna

        """

        # we may need to actually resample as if we are timestamps
        if self.kind == 'timestamp':
            return super()._upsample(method, limit=limit,
                                     fill_value=fill_value)

        self._set_binner()
        ax = self.ax
        obj = self.obj
        new_index = self.binner

        # Start vs. end of period
        memb = ax.asfreq(self.freq, how=self.convention)

        # Get the fill indexer
        indexer = memb.get_indexer(new_index, method=method, limit=limit)
        return self._wrap_result(_take_new_index(
            obj, indexer, new_index, axis=self.axis))