<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def callback(self, position):
 """ Allows the execution of custom code between creation of the zip file and deployment to AWS. :return: None """


        callbacks = self.stage_config.get('callbacks', {})
        callback = callbacks.get(position)

        if callback:
            (mod_path, cb_func_name) = callback.rsplit('.', 1)

            try:  # Prefer callback in working directory
                if mod_path.count('.') >= 1:  # Callback function is nested in a folder
                    (mod_folder_path, mod_name) = mod_path.rsplit('.', 1)
                    mod_folder_path_fragments = mod_folder_path.split('.')
                    working_dir = os.path.join(os.getcwd(), *mod_folder_path_fragments)
                else:
                    mod_name = mod_path
                    working_dir = os.getcwd()

                working_dir_importer = pkgutil.get_importer(working_dir)
                module_ = working_dir_importer.find_module(mod_name).load_module(mod_name)

            except (ImportError, AttributeError):

                try: # Callback func might be in virtualenv
                    module_ = importlib.import_module(mod_path)
                except ImportError: # pragma: no cover
                    raise ClickException(click.style("Failed ", fg="red") + 'to ' + click.style(
                        "import {position} callback ".format(position=position),
                        bold=True) + 'module: "{mod_path}"'.format(mod_path=click.style(mod_path, bold=True)))

            if not hasattr(module_, cb_func_name): # pragma: no cover
                raise ClickException(click.style("Failed ", fg="red") + 'to ' + click.style(
                    "find {position} callback ".format(position=position), bold=True) + 'function: "{cb_func_name}" '.format(
                    cb_func_name=click.style(cb_func_name, bold=True)) + 'in module "{mod_path}"'.format(mod_path=mod_path))


            cb_func = getattr(module_, cb_func_name)
            cb_func(self)