Load data, from default location

        Returns:
            pandas.DataFrame: columns 'key' (NUTS2 code), 'name'

def load(self):
        """Load data, from default location

        Returns:
            pandas.DataFrame: columns 'key' (NUTS2 code), 'name'
        """
        # read file, keep all values as strings
        df = pd.read_csv(self.input_file,
                         sep=',',
                         quotechar='"',
                         encoding='utf-8',
                         dtype=object)

        # wer are only interested in the NUTS code and description, rename them also
        df = df[['NUTS-Code', 'Description']]
        df.columns = ['key', 'name']

        # we only want NUTS2 regions (4-digit codes)
        df = df[df['key'].str.len() == 4]

        # drop 'Extra Regio' codes ending in 'ZZ'
        df = df[df['key'].str[2:] != 'ZZ']

        return df