Loads a workflow identified by id_code
        id_code - unique identifier, previously must have called save with same id_code

def load(self, id_code):
        """
        Loads a workflow identified by id_code
        id_code - unique identifier, previously must have called save with same id_code
        """
        filestream = open('{0}/{1}'.format(self.data_path, id_code), 'rb')
        workflow = pickle.load(filestream)
        return workflow