code: def __post_init__(self):
      if isinstance(self.axis, int):
          self.axis = (self.axis,)
  
file_path: gluonts/src/gluonts/ev/aggregations.py
imports: from dataclasses import dataclass
  from typing import List, Optional, Union
  import numpy
label_desc: Use image node_id 1 for calling the Aggregation obj's underlying member method code with example usage: obj.__post_init__() without return types