code: def _combine_input_and_mask(
      op, input: Union[MaskedTensor, Tensor], mask, *args
  ) -> Tensor:
      def helper(input, mask):
          if mask is None:
              return input
          canonical_mask = _input_mask(input, mask=mask)
          if callable(op):
              fill_value = _reduction_identity(
                  op.__name__, input, *args
              )
              return _where(canonical_mask, input, fill_value)
          else:
              raise ValueError(
                  f"_combine_input_and_mask expected masked operation (got {type(op).__name__} object)"
              )
  
      class Combine(torch.autograd.Function):
          @staticmethod
          def forward(ctx, input, mask):
              """Return input with masked-out elements eliminated for the given operations."""
              ctx.save_for_backward(mask)
  
              if mask is not None:
                  ctx.mark_non_differentiable(mask)
  
              return helper(input, mask)
  
          @staticmethod
          def backward(ctx, grad_output):
              (mask,) = ctx.saved_tensors
              grad_data = (
                  grad_output.get_data()
                  if is_masked_tensor(grad_output)
                  else grad_output
              )
              result = as_masked_tensor(grad_data, mask)
              return result, None
  
      return (
          Combine.apply(input.get_data(), input.get_mask())  # type: ignore[union-attr]
          if is_masked_tensor(input)
          else helper(input, mask)
      )
  
imports: import warnings
  from typing import Any, List, Optional, Tuple, TYPE_CHECKING, Union
  import torch
  from torch import Tensor
  from torch.masked import as_masked_tensor, is_masked_tensor, MaskedTensor
  from .None import _docs
  from torch._prims_common import corresponding_real_dtype
  from torch import sym_float
label_desc: Use image node_id 14 for calling a global function with example usage: _combine_input_and_mask(op, input, mask) and returns: unknown, input, _where, helper, result,  None