class_docstr: Link that holds a temperature as a learnable value.
  
  Args:
      initial_log_temperature (float): Initial value of log(temperature).
docstr: Return a temperature as a chainer.Variable.
code: def __call__(self):
      """Return a temperature as a chainer.Variable."""
      return F.exp(self.log_temperature)
  
imports: import collections
  import copy
  from logging import getLogger
  import chainer
  from chainer import cuda
  import chainer.functions
  import numpy
  from chainerrl.agent import AttributeSavingMixin
  from chainerrl.agent import BatchAgent
  from chainerrl.misc.batch_states import batch_states
  from chainerrl.misc.copy_param import synchronize_parameters
  from chainerrl.replay_buffer import batch_experiences
  from chainerrl.replay_buffer import ReplayUpdater
label_desc: Use image node_id 2 for calling the TemperatureHolder obj's underlying member method code with example usage: obj.__call__() and returns: F