def load(self, steps_dir=None, step_file=None, step_list=None):
        """Load CWL steps into the WorkflowGenerator's steps library.

        Adds steps (command line tools and workflows) to the
        ``WorkflowGenerator``'s steps library. These steps can be used to
        create workflows.

        Args:
            steps_dir (str): path to directory containing CWL files. All CWL in
                the directory are loaded.
            step_file (str): path to a file containing a CWL step that will be
                added to the steps library.
        """
        self._closed()

        self.steps_library.load(steps_dir=steps_dir, step_file=step_file,
                                step_list=step_list)