code: def __post_init__(self) -> None:
      assert len(self.by) == len(
          set(self.by)
      ), f"'by' must have unique values. Found {self.by}."
  
imports: import heapq
  from dataclasses import dataclass
  from enum import Enum
  from typing import Any, Collection, Iterator, List, Sequence, Tuple, Type
  import pandas
  from benchmark.metadata import BenchmarkMetadata
  from benchmark.plotter_api import Plotter
label_desc: Use image node_id 1 for calling the GroupingSpec obj's underlying member method code with example usage: obj.__post_init__() without return types