How to create custom dataset with following function?

I want to create a custom dataset where I can read a CSV file and do the following lambda function. I have created a part of the class but I am getting an error for the map and concatenate function.

AttributeError: 'ConcatDataset' object has no attribute 'map'
AttributeError: 'map' object has no attribute 'map'
This is my dataset class.
class MyDataset(Dataset):
    def __init__(self, csv_path):
        self.df = pd.read_csv(csv_path, index_col=False)

    def __getitem__(self, index):
        return self.df.iloc[index, :].to_dict()

    def __len__(self):
        return len(self.df)

    def map(self, func):
        return map(func, self)

    def concatenate(self, dataset):
        # cocatenate dataset

I want to do the following;

mydataset = MyDataset("train_data.csv")
datasets = []
for k in range(5):
    datasets.append( x: some_function)

dataset = datasets[-1]
for d in datasets[:-1]:
    dataset = dataset.concatenate(d)


# again do mapping 
dataset = x: x ** 2)
# and also some other functions like

From what I understood the error is coming because the function is not returning the object of the same class.

Thanks in advance!