code: def task_generator(tasks, generators) -> list:
      """
      Use a list of TaskGen and a list of task templates to generate different tasks.
  
      For examples:
  
          There are 3 task templates a,b,c and 2 TaskGen A,B. A will generates 2 tasks from a template and B will generates 3 tasks from a template.
          task_generator([a, b, c], [A, B]) will finally generate 3*2*3 = 18 tasks.
  
      Parameters
      ----------
      tasks : List[dict] or dict
          a list of task templates or a single task
      generators : List[TaskGen] or TaskGen
          a list of TaskGen or a single TaskGen
  
      Returns
      -------
      list
          a list of tasks
      """
  
      if isinstance(tasks, dict):
          tasks = [tasks]
      if isinstance(generators, TaskGen):
          generators = [generators]
  
      # generate gen_task_list
      for gen in generators:
          new_task_list = []
          for task in tasks:
              new_task_list.extend(gen.generate(task))
          tasks = new_task_list
  
      return tasks
  
imports: import abc
  import copy
  import pandas
  from typing import Dict, List, Union, Callable
  from qlib.utils import transform_end_date
  from .utils import TimeAdjuster
label_desc: Use image node_id 1 for calling a global function with example usage: task_generator(tasks, generators) and returns: tasks