docs: def lazy_import(module_name, to_import):
      """Return the importing module and a callable for lazy importing.
  
      The module named by module_name represents the module performing the
      import to help facilitate resolving relative imports.
  
      to_import is an iterable of the modules to be potentially imported (absolute
      or relative). The `as` form of importing is also supported,
      e.g. `pkg.mod as spam`.
  
      This function returns a tuple of two items. The first is the importer
      module for easy reference within itself. The second item is a callable to be
      set to `__getattr__`.
      """
      module = importlib.import_module(module_name)
      import_mapping = {}
      for name in to_import:
          importing, _, binding = name.partition(' as ')
          if not binding:
              _, _, binding = importing.rpartition('.')
          import_mapping[binding] = importing
  
      def __getattr__(name):
          if name not in import_mapping:
              raise ModuleAttributeError(module_name, name)
          importing = import_mapping[name]
          # imortlib.import_module() implicitly sets submodules on this module as
          # appropriate for direct imports.
          imported = importlib.import_module(importing,
                                             module.__spec__.parent)
          setattr(module, name, imported)
          return imported
  
      return module, __getattr__