class_docstr: A collection of variables used by subclasses of `MixtureAgent`.
  
  Note that this variable collection only contains the mixture weights. The
  variables of the sub-agents that the mixture agent mixes are in variable
  collections of the respective sub-agents.
code: def reward_aggregates(self):
      return self._reward_aggregates
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from typing import List, Optional, Text
  import gin
  import tensorflow
  import tensorflow_probability
  from tf_agents.agents import tf_agent
  from tf_agents.bandits.agents import mixture_agent
  from tf_agents.bandits.policies import mixture_policy
  from tf_agents.utils import nest_utils
label_desc: Use image node_id 2 for calling the Exp3MixtureVariableCollection obj's underlying member method code with example usage: obj.reward_aggregates() and returns: self