def _classify_data_by_type(self, order, skip=[]):
        d = dict()
        for typ in order:
            d[typ] = []

        for column_name in self.data:
            if column_name not in skip:
                typ = infer_vegalite_type(self.data[column_name])
                d[typ].append(column_name)

        return d
Get O, N, Q, or T vegalite type for all columns in data except if in skip.
dataset/ETHPy150Open ellisonbg/altair/altair/api.py/Viz._classify_data_by_type