import torch
from torch.utils.data import DataLoader, Dataset


class SampleDataset(Dataset):
    def __init__(self):
        self.records = [
            [0.10, 0.20, 0.30],
            [0.60, 0.40, 0.90],
            None,
            [0.20, 0.70, 0.50],
        ]

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

    def __getitem__(self, index):
        values = self.records[index]
        if values is None:
            raise ValueError(f"record {index} has no feature values")
        return torch.tensor(values, dtype=torch.float32)