code: def sum_of_squared_diffs_from_mean(
      self,
      on: str,
      ignore_nulls: bool,
      mean: Optional[U] = None,
  ) -> Optional[U]:
      if mean is None:
          mean = self.mean(on, ignore_nulls)
      return self._apply_agg(
          lambda col: ((col - mean) ** 2).sum(skipna=ignore_nulls),
          on,
      )
  
imports: import collections
  import heapq
  from typing import TYPE_CHECKING, Any, Callable, Dict, Iterator, List, Optional, Tuple, TypeVar, Union
  import numpy
  from ray.air.constants import TENSOR_COLUMN_NAME
  from ray.data._internal.table_block import TableBlockAccessor, TableBlockBuilder
  from ray.data._internal.util import find_partitions
  from ray.data.block import Block, BlockAccessor, BlockExecStats, BlockMetadata, KeyType, U
  from ray.data.context import DataContext
  from ray.data.row import TableRow
label_desc: Use image node_id 25 for calling the PandasBlockAccessor obj's underlying member method code with example usage: obj.sum_of_squared_diffs_from_mean(on, ignore_nulls, mean) and returns: self