code: def set_default_dtype(value):
      """Set backend default dtype.
  
      Parameters
      ----------
      value : str
          Possible values are "float32" as "float64".
      """
      _config.DEFAULT_DTYPE = as_dtype(value)
      _config.DEFAULT_COMPLEX_DTYPE = as_dtype(
          _MAP_FLOAT_TO_COMPLEX.get(value)
      )
      _torch.set_default_dtype(_config.DEFAULT_DTYPE)
  
      _update_default_dtypes()
  
      return _config.DEFAULT_DTYPE
  
file_path: geomstats/geomstats/_backend/pytorch/_dtype.py
imports: import functools
  import torch
  from torch import complex64, complex128, float32, float64
  from geomstats._backend import _backend_config
  from geomstats._backend._dtype_utils import _MAP_FLOAT_TO_COMPLEX, _modify_func_default_dtype, _pre_add_default_dtype_by_casting, _pre_allow_complex_dtype, _pre_cast_out_to_input_dtype, _update_default_dtypes, get_default_cdtype, get_default_dtype
  from ._common import cast
label_desc: Use image node_id 6 for calling a global function with example usage: set_default_dtype(value) and returns: _config