Make Data class derive from pandas.DataFrame

This will simplify the usage of class Data in method TimePane.add_data.

This is a possible code:

import pandas as pd


class Data(pd.DataFrame):
    def __init__(self, filename, file_format, current_format):
        super().__init__(pd.read_csv(filename, sep=None, engine="python"))
        self.update_format(file_format, current_format)

    def update_format(self, file_format, current_format):
        for fmt in range(file_format + 1, current_format + 1):
            if fmt == 2:
                pass
            if fmt == 3:
                self.rename(columns={"label": "event"}, inplace=True)