code: def _build_backend():
      
      ep = os.environ['PEP517_BUILD_BACKEND']
      mod_path, _, obj_path = ep.partition(':')
      try:
          obj = import_module(mod_path)
      except ImportError:
          raise BackendUnavailable
      if obj_path:
          for path_part in obj_path.split('.'):
              obj = getattr(obj, path_part)
      return obj
docs: Find and load the build backend