TypeError: stack(): argument 'tensors' (position 1) must be tuple of Tensors, not Tensor

This error occurs when the `stack()` function in PyTorch is called with a single tensor instead of a tuple of tensors.

To resolve this error, you need to pass a tuple of tensors to the `stack()` function instead of a single tensor. For example:

import torch

# Create two tensors
tensor1 = torch.tensor([1, 2, 3])
tensor2 = torch.tensor([4, 5, 6])

# Use stack() function to stack the tensors
stacked_tensors = torch.stack((tensor1, tensor2))

print(stacked_tensors)

This will output:

tensor([[1, 2, 3],
        [4, 5, 6]])

Notice that we passed a tuple of tensors `(tensor1, tensor2)` to the `stack()` function.