How to use the b2luigi.core.utils function in b2luigi

def exists(self):
        if not super().exists():
            return False

        try:
            import ROOT
        except ImportError:
            raise ImportError("Can not import ROOT. The ROOTLocalTarget can not be used!")

        path = self.path
        tfile = ROOT.TFile.Open(path)
        return tfile and len(tfile.GetListOfKeys()) > 0


class Task(luigi.Task, TaskWithDataSupport):
    git_hash = luigi.Parameter(default=utils.get_basf2_git_hash())

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        filename = os.path.realpath(sys.argv[0])
        log_folder = os.path.join(os.path.dirname(filename), "logs")
        stdout_file_name = self.get_output_file_name(self.get_task_family() + "_stdout", create_folder=True,
                                                     result_path=log_folder)

        stderr_file_name = self.get_output_file_name(self.get_task_family() + "_stderr", create_folder=True,
                                                     result_path=log_folder)

        self.log_files = {"stdout":  stdout_file_name,
                          "stderr": stderr_file_name,
                          "log_folder": log_folder}

def _transform_input(input_generator, key=None):
        input_list = utils.flatten_to_list_of_dicts(input_generator)
        file_paths = utils.flatten_to_file_paths(input_list)

        if key is not None:
            return file_paths[key]
        else:
            return file_paths