old_contents: class DevicePositionMixin():
      @property
      def x(self):
          return self.config.get('x', None)
  
      @property
      def y(self):
          return self.config.get('y', None)
  
      @property
      def z(self):
          return self.config.get('z', None)
  
new_contents: """Device Mixins."""
  
  
  class DevicePositionMixin():
  
      """Adds x/y/z getters to a device.
  
      For devices that have x/y/z config in the yaml this
      mixin will add getters to allow the use of device.x
      device.y and device.z instead of device.config['x']
      """
  
      @property
      def x(self):
          """Get the X value from the config.
  
          Returns the devices x position from config
          """
          return self.config.get('x', None)
  
      @property
      def y(self):
          """Get the Y value from the config.
  
          Returns the devices y position from config
          """
          return self.config.get('y', None)
  
      @property
      def z(self):
          """Get the Z value from the config.
  
          Returns the devices z position from config
          """
          return self.config.get('z', None)
  
subject: Fix up docstrings in mpf/devices/device_mixins.py