docstr: Return list of gradient slices of a specific parameter
  
  Args:
      group_id (int): The index of a parameter group
      param_id (int): The id of a parameter
  
  Returns:
      List: the list of gradient slices of a parameter.
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code: def get_partitioned_gradients_by_param_id(
      self, group_id: int, param_id: int
  ) -> List:
      """Return list of gradient slices of a specific parameter
  
      Args:
          group_id (int): The index of a parameter group
          param_id (int): The id of a parameter
  
      Returns:
          List: the list of gradient slices of a parameter.
      """
  
      if group_id in self._grads_of_params:
          if param_id in self._grads_of_params[group_id]:
              return self._grads_of_params[group_id][param_id]
      # the param has no grad, for instance, in layer drop
      return []
  
file_path: ColossalAI/colossalai/zero/low_level/bookkeeping/gradient_store.py
imports: from typing import List
  from torch import Tensor
  from .base_store import BaseStore
label_desc: Use image node_id 2 for calling the GradientStore obj's underlying member method code with example usage: obj.get_partitioned_gradients_by_param_id(group_id, param_id) and returns: list, self