class_docstr: Accumulator for sum aggregation.
  
  Attributes:
    sum: The sum of the input values.
docstr: Merges the accumulator to self and returns self.
  
  Args:
    accumulator: Another accumulator of the same type to merge.
  
  Returns:
    self
code: def add_accumulator(
      self, accumulator: "SumAccumulator"
  ) -> "SumAccumulator":
      """Merges the accumulator to self and returns self.
  
      Args:
        accumulator: Another accumulator of the same type to merge.
  
      Returns:
        self
      """
      self._check_mergeable(accumulator)
      self.sum += accumulator.sum
      return self
  
imports: import abc
  from typing import Any, List, Sequence
  import pipeline_dp
label_desc: Use image node_id 3 for calling the SumAccumulator obj's underlying member method code with example usage: obj.add_accumulator(accumulator) and returns: self