def mappings(self, year=None):
        raise NotImplementedError()
Returns csv data as a pandas Dataframe object
dataset/ETHPy150Open openelections/openelections-core/openelex/base/datasource.py/BaseDatasource.mappings--crossover with--dataset/ETHPy150Open Azure/Azure-MachineLearning-ClientLibrary-Python/azureml/serialization.py/_dataframe_from_csv