class_docstr: A class that acts as linear reward function when called.
code: def __init__(self, theta, sigma):
      self.theta = theta
      self.sigma = sigma
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import functools
  import gin
  import numpy
  from six.moves import range
  import tensorflow
  from tf_agents.bandits.agents import utils
  from tf_agents.bandits.environments import wheel_py_environment
label_desc: Use image node_id 1 to create a new LinearNormalReward object from inherited base classes: object with example: obj = LinearNormalReward(theta, sigma)