Load all project Task Runs from Tasks.

def get_task_runs(self, json_file=None):
        """Load all project Task Runs from Tasks."""
        if self.project is None:
            raise ProjectError
        loader = create_task_runs_loader(self.project.id, self.tasks,
                                         json_file, self.all)
        self.task_runs, self.task_runs_file = loader.load()

        self._check_project_has_taskruns()
        self.task_runs_df = dataframer.create_task_run_data_frames(self.tasks, self.task_runs)