new_contents: class SharpIrDistanceSensor(object):
  
      def __init__(self, spi_interface, pin_id):
          self.spi_interface = spi_interface
          self.pin_id = pin_id
  
      def _voltageToMeters(self, voltage):
          return 67.84 / (voltage - 3) - 0.04
  
      def readDistance(self):
          '''Returns distance in meters.'''
          voltage = self.spi_interface.read(self.pin_id)
          distance = self._voltageToMeters(voltage)
          return distance
  
subject: Add implementation for Sharp IR distance sensor