
end_dim (int) -- the last dim to flatten

Example:
  >>> t = torch.tensor([[[1, 2],
  ...                    [3, 4]],
  ...                   [[5, 6],
  ...                    [7, 8]]])
  >>> torch.flatten(t)
  tensor([1, 2, 3, 4, 5, 6, 7, 8])
  >>> torch.flatten(t, start_dim=1)
  tensor([[1, 2, 3, 4],
          [5, 6, 7, 8]])
