code: def _mirror_index_fixer(index, size):
      s = size - 1  # Half-wavelength of triangular wave
      # Scaled, integer-valued version of the triangular wave |x - round(x)|
      return torch.abs((index + s) % (2 * s) - s)
  
file_path: keras/keras/backend/torch/image.py
imports: import functools
  import itertools
  import operator
  import torch
  from keras.backend.torch.core import convert_to_tensor
label_desc: Use image node_id 3 for calling a global function with example usage: _mirror_index_fixer(index, size) and returns: torch