torch::Tensor to caffe2::Tensor

To convert a `torch::Tensor` to a `caffe2::Tensor`, you can use the `caffe2::TensorCPU` class, which provides a constructor that takes a pointer to data and a vector of dimensions. Here's an example:

#include <caffe2/core/tensor.h>
#include <torch/torch.h>

int main() {
  // Create a torch::Tensor
  torch::Tensor t = torch::ones({2, 3});

  // Convert to a caffe2::Tensor
  caffe2::TensorCPU c2_tensor((float*)t.data_ptr(), {2, 3});

  return 0;
}

In this example, we create a `torch::Tensor` with dimensions 2x3 and fill it with ones. Then, we pass a pointer to the data and the dimensions to the `caffe2::TensorCPU` constructor to create a `caffe2::Tensor`. Note that we cast the data pointer to a `float*` because `caffe2::TensorCPU` expects a pointer to float data.