Learner training Error when using databunch created from pytorch dataset

I am getting myself familiarized with FastAI library.
I would like to practice creating data bunch directly off PyTorch dataset.

My dataset : X = image Y = binary label (0 or 1)

My dataset and databunch

import os
import torch
import pandas as pd
from skimage import io, transform
import numpy as np
import matplotlib.pyplot as plt
from torch.utils.data import Dataset, DataLoader
from torchvision import transforms
import cv2
# plt.ion()

class HotOrNotDataset(Dataset):
  def __init__(self, csv_file, img_root, transform=None):
    self.ratings = pd.read_csv(csv_file)
    self.img_root = img_root 
    self.transform = transform 
    self.c = 1
    self.loss_func = BCEFlat()

  def __len__(self): 
    return len(self.ratings)
  def __getitem__(self, idx):
    img_name = os.path.join(self.img_root,
    image = cv2.imread(img_name)
    image = image / 255.0
    target = self.ratings.iloc[idx]['Hot']
    ## Tagret is 0 or 1
    sample = (image, target)

    if self.transform:
            sample = self.transform(sample)
    return sample

class ToTensor(object):
    """Convert ndarrays in sample to Tensors."""

    def __call__(self, sample):
        image, label = sample
        image = image.transpose((2, 0, 1))
        return (torch.from_numpy(image).float(), torch.from_numpy(np.array([label])).long())

class Normalize(object):
     def __init__(self):
       self.normalize = transforms.Normalize(mean=[0.485, 0.456, 0.406],
                                 std=[0.229, 0.224, 0.225])
     def __call__(self, x):
       image, label = x
       return (self.normalize(image), label)
dataset = HotOrNotDataset(csv_file='ratings.csv',

db = DataBunch.create(dataset, dataset)

Training with learner:

# Bare minimum learner
import torchvision.models as models
model=models.mobilenet_v2(pretrained=True, progress=True)
for param in model.parameters():
    param.requires_grad = False
new_head = nn.Sequential(nn.Dropout(p=0.2,inplace=False),
model.classifier = new_head

learn = Learner(db, model, metrics=[accuracy])

Got the error “Error: multi-target not supported at /pytorch/aten/src/THCUNN/generic/ClassNLLCriterion.cu:15”

What am I doing wrong here?
Is the problem with dataset & databunch creation or it is something else?

Appreciate your help and support