code: def set_backend(_backend):
      """Use this method to switch sparse backend dynamically. When importing this module with a wildcard such as
      from torch_points3d.modules.SparseConv3d.nn import *
      make sure that you import it again after calling this method.
  
  
      Parameters
      ----------
      backend : str
          "torchsparse" or "minkowski"
      """
      assert backend_valid(_backend)
      try:
          modules = importlib.import_module(
              "." + _backend, __name__
          )  # noqa: F841
          global sp3d_backend
          sp3d_backend = _backend
      except:
          log.exception(
              "Could not import %s backend for sparse convolutions"
              % _backend
          )
      for val in __all__:
          exec("globals()['%s'] = modules.%s" % (val, val))
  
imports: import os
  import sys
  import logging
  import importlib
label_desc: Use image node_id 3 for calling a global function with example usage: set_backend(_backend) without return types