old_contents: 
  import random
  
  class Sensor(object):
      OFFSET = 16
          
      def pop_next_pressure_psi_value(self):
          pressure_telemetry_value = self.sample_pressure()
          return Sensor.OFFSET + pressure_telemetry_value
  
      @staticmethod
      def sample_pressure():
          # placeholder implementation that simulate a real sensor in a real tire
          pressure_telemetry_value = 6 * random.random() * random.random()
          return pressure_telemetry_value
  
  
  class Alarm(object):
  
      def __init__(self):
          self._low_pressure_threshold = 17
          self._high_pressure_threshold = 21
          self._sensor = Sensor()
          self.is_alarm_on = False
          self._alarm_count = 0
  
      def check(self):
          psi_pressure_value = self._sensor.pop_next_pressure_psi_value()
          if psi_pressure_value < self._low_pressure_threshold or self._high_pressure_threshold < psi_pressure_value:
              self.is_alarm_on = True
              self._alarm_count += 1
  
new_contents: 
  import random
  
  class Sensor(object):
      OFFSET = 16
          
      def pop_next_pressure_psi_value(self):
          pressure_telemetry_value = self.sample_pressure()
          return Sensor.OFFSET + pressure_telemetry_value
  
      @staticmethod
      def sample_pressure():
          # placeholder implementation that simulate a real sensor in a real tire
          pressure_telemetry_value = 6 * random.random() * random.random()
          return pressure_telemetry_value
  
  
  class Alarm(object):
  
      def __init__(self):
          self._low_pressure_threshold = 17
          self._high_pressure_threshold = 21
          self._sensor = Sensor()
          self._is_alarm_on = False
          
      def check(self):
          psi_pressure_value = self._sensor.pop_next_pressure_psi_value()
          if psi_pressure_value < self._low_pressure_threshold or self._high_pressure_threshold < psi_pressure_value:
              self._is_alarm_on = True
  
      @property
      def is_alarm_on(self):
          return self._is_alarm_on
  
subject: make is_alarm_on into a property to protect it from being written to. Thanks to neppord for the suggestion