code: def _get_reduction_string(size_average, reduce):
      if size_average is None:
          size_average = True
      if reduce is None:
          reduce = True
      if size_average and reduce:
          ret = "mean"
      elif reduce:
          ret = "sum"
      else:
          ret = "none"
      return ret
  
imports: import ivy
  import ivy.functional.frontends.torch
  from ivy.functional.frontends.torch.func_wrapper import to_ivy_arrays_and_back
  from ivy.func_wrapper import with_unsupported_dtypes, with_supported_dtypes
label_desc: Use image node_id 5 for calling a global function with example usage: _get_reduction_string(size_average, reduce) and returns: ret