That’s odd, I’m using the same code but slightly simplified for imports:
class MyOwnDataset():
    def __init__(self, input_data_paths):
        self.raw_file_names = input_data_paths
    
    @property
    def raw_file_names(self):
        return self.__raw_file_names

    @raw_file_names.setter
    def raw_file_names(self, value):
        self.__raw_file_names = value

ds = MyOwnDataset('asdf')
print(ds.raw_file_names)
# >> 'asdf'