code: def summed_y(self) -> float:
      if self.y_sum_cache_up_to_date:
          return self._summed_y
      else:
          self._summed_y = np.sum(self._y * self._inverse_mask_int)
          self.y_sum_cache_up_to_date = True
          return self._summed_y
  
imports: from operator import gt, le
  from typing import Any, List, Optional, Union
  import numpy
  import pandas
  from .errors import NoSplittableVariableException
  from .splitcondition import SplitCondition
label_desc: Use image node_id 6 for calling the Target obj's underlying member method code with example usage: obj.summed_y() and returns: self, self