class_docstr: Abstract base class for combining the outputs of multiple models. Subclasses
  should implement the abstract method ``_combine_univariates``. All combiners
  are callable objects.
  
  .. automethod:: __call__
code: def _combine_univariates(
      self, univariates: List[UnivariateTimeSeries]
  ):
      raise NotImplementedError
  
imports: from abc import abstractmethod
  from collections import OrderedDict
  import copy
  import logging
  from typing import List, Optional, Union
  import numpy
  from merlion.evaluate.anomaly import TSADMetric
  from merlion.evaluate.forecast import ForecastMetric
  from merlion.utils import UnivariateTimeSeries, TimeSeries
  from merlion.utils.misc import AutodocABCMeta
label_desc: Use image node_id 8 for calling the CombinerBase obj's underlying member method code with example usage: obj._combine_univariates(univariates) without return types