model UserWarning: torch.meshgrid: in an upcoming release, it will be required to pass the indexing argument. return forward_c

The `UserWarning` message you're seeing is related to a change that will be introduced in a future version of PyTorch, specifically when using the `torch.meshgrid` function. This function is used for creating a grid of coordinates for multidimensional arrays, often in the context of tensor operations like convolutions or broadcasting.

The warning suggests that starting from a certain version, the indexing argument will be mandatory when calling `torch.meshgrid`. This is likely to enforce more explicit control over how the indexing is handled. The `forward_c` in the warning might refer to some custom or internal function within your code that uses this function.

Here's what you can do to address this warning:
1. Check the documentation for the specific version you're using and see if there's a recommended way to update your code.
2. Add the indexing argument explicitly when calling `torch.meshgrid`. The syntax usually looks like this: `meshgrid = torch.meshgrid(*arrays, indexing='ij')`, where 'ij' is the default indexing mode (row-major order).
3. If you're not using any indexing customization, you can suppress the warning by wrapping the call with `torch.no_grad()` or `warnings.filterwarnings('ignore', category=UserWarning)` but it's generally better to fix the code.