text: from abc import abstractmethod, ABCMeta
  
  
  class BaseSensor():
      """
      Base Sensor class.
      Sensor-specific get_obs method is implemented in subclasses
      """
      __metaclass__ = ABCMeta
      def __init__(self, env):
          self.config = env.config
  
      @abstractmethod
      def get_obs(self, env):
          """
          Get sensor reading
  
          :param: environment instance
          :return: observation (numpy array or a dict that maps str to numpy array)
          """
          raise NotImplementedError()
  